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Hello everyone.



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So in this video we will create our own copy constructor.



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So before writing our own copy constructor let us analyze again how in built copy constructor works.



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Okay.



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So let us comment out discord



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okay.



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So let us make a copy first.



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So we have a student as to and as to his copy of S1 so at this line copy constructor will be called.



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Okay so a copy constructor called



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Okay so now let us change the name of S2.



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So let us change it since you wrote the index to X



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okay.



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So the named properties are private property.



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So to exist name let us make name is public.



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Okay.



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We can also use good enter the function.



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But for simplicity I made the name variable a public field.



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Okay.



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So after changing the name for as to student S2.



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Now let us print s Fernandez too.



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So as S1 not display function and similarly S2 dart display.



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Okay so no one here does in this file.



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Okay so let's send this file



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so not display Okay so completion edit



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see both attorneys to both the names are X BCE which is wrong.



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Okay so the student one name also word changed.



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If I changed the name of the student to so let us try to analyze what is happening here.



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Ideally the name for a student I think should be ABC but it is getting changed to X obesity.



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Okay so let's try to understand why why it is happening



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so let's say this name contains that the seven ended and we have a b c d and then so that beat us off



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is seven.



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Okay now when we call paramedics constructor what will happen.



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So age will become 20 and since we have made deep copy so the name will contain and address the 800.



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So this is our S1 and 800 is the address of a b c d.



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And then an so we.



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Can you stay the course in deep copy we make a new area.



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And then this name will contain their address.



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800 so this is the content here.



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Okay.



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We copied this content now what will happen at this line.



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Copy constructively recalled so I'd copy constructor will do.



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It will create a new object with the name as to so each will get copied so each will become 20 and the



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name will also get copied the name will contain 800.



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So what is happening here is the name of S1 is pointing towards this memory location and the name of



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S2 is also pointing towards this remote location.



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So basically what is happening here is copy constructor makes shallow copy.



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Ok this fellow copy is being made shallow copy is created by inbuilt copy constructor



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so always remember our inbuilt court because our inbuilt copy constructor always makes shallow copy.



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Okay so at this land line number be what we are trying to do we are changing the zero to next to x.



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So go to 800 number location and then change the zero to next to x.



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So then we are printing and as for not displaying astronaut display.



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So I started our display will print this one so x BCG and similarly astronaut display will go to address



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800 and and we will print.



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So that's why X BSD okay.



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So that's why SBC didn't explicitly I'd bring 34 S1 and S2 okay because I went and made copy.



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That's a big read shallow copy.



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So whenever we have dynamic Eddie as our data member as our property so we should always create our



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own copy goes to third to a wide shallow copy.



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So when we will create our own copy constructor we will do beep copy.



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Okay so it is important here it is.



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It is very important here for us to create our own copy construct because we do not want shallow copy.



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We want deep copy and inbuilt copy precludes shallow copy.



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That's why we have to create our own copy construct bit here.



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So it is mandatory here.



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It is not a choice.



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It is amended reader's compulsion.



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Okay.



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We have to.



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We have to create copy construct but we have to create our own copy construct that here.



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Okay.



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So creating the copy I stepped over to the structure so the structure is first of all.



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Same name as the last name same name as the last name.



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What it will take it will take us to an end as input.



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So student s and then what it will do it will copy the age Endy name.



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So this A2 age is as dotage and this ETL name is as not name.



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Okay so this is shallow copy this is shallow copy we are only copying the address.



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So this is how inbuilt copy the script that is written.



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Okay so this is in made copy constructor This is the code for and built copy constructor but since we



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have to create a deep copy since we have to create the copy what we will do we will make a new area



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and then we will copy the content so this Edwin name is New get now what would it be the land string



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lint off s dart name.



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And we have to loop plus one by plus one because we have to copy Mello also and then we will use string



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copy function state copy function we will give this ATL name and start name.



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Okay so in this way we will create our own DB copy.



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So this is the code for deep copy



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deep copy.



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Okay.



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Now what will happen.



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So this is our name from the mean.



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This convinced that this seven hundred and I will lose a b c d and then



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now we have our S1 so S1 contains h to be 20 and named 2B 800 y 800 because we created our new Eddie



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and then we copied the content and the address of this new ad is 800.



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Okay.



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So the name of S1 points towards this primary location.



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Now let us talk about the copy constructor so we'll copy constructor we are creating a new object with



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the name S2.



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So first of all we will copy that each.



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So each will become 20 and then what we are trying to do here is we are creating a new edit.



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So when you add it will get created the size will be 5 and then what we are trying to do we are copying



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the content.



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So a b c d and then let's say the address is 900.



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So this time the name of S2 is containing the address nine hundred.



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So if I will change the name of S2 If I will make it s x then there will be no effect on the name of



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S1 so when eventually write as front our display then ABC the printed there then we will write astronaut



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display.



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Then explicitly got printed.



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Okay so this is deep copy and how we will call our constructor student as to in Port argument S1 so



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this has to be going this and this S1 will be as a barometer.



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Okay.



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This S1 will be as a barometer.



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Okay so according to me everything seems fine but everything is not fine.



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Okay.



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Why does not fine.



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There is a very big mistake that we are doing here is let's try to understand what is the mistake that



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we are that I am talking about.



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So what happened is when you light student S2 S1 so this will go in this function of the copy constructor



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and S1 will come here.



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So a copy will be created.



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So over so we can write.



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We can write this line is student s is main dot S1 okay S1 from the mean is being incompetent to student



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s and in the previous we do as we have learned whenever we write student s three close S1.



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So although this is copy assignment operator.



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But we know copy constructor will be called here.



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We have already discussed about it in the previous videos.



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So copy constructor will be called here.



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Okay so at this line copy constructor is being getting called Okay by a copy constructor is being recalled



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because we are passing values by value.



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Okay.



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This is passed by values and although this is not correct this is not correct.



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Why.



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This is not correct.



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Why this is not correct because this is not valid because as soon as we create our own copy constructor



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and will copy construct is not available to us anymore.



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Just like as soon as we write our own default constructor that inbuilt default constructor goes away.



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Likewise as soon as we create our own copy constructor the inbuilt copy constructor is not available



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to us anymore.



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So what really happened at this line we are calling copy constructor so in bulk does not available so



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our copy constructively regardless.



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So this will call our own copy constructor okay and then we will come to this argument and as we come



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to this argument copy construct every get called to copy the values from S1 to s..



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Okay so in this way infinite loop will be created in finite loop will be created.



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Why.



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Because first of all copy constructively but call here to copy the values from S1 to s and then then



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we will reach this argument then a game copy constructor will be called and our copy can certainly be



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called because we have write our own copy constructors when will construct but is not available to us



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anymore so why.



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That's why infinite loop is here so why infinite loop because we are talking about creating copy constructor



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and in the argument of that copy constructor we need a copy constructor okay I'm repeating myself.



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So we're creating a copy constructor and to create copy constructor we need to copy constructor in the



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argument to copy the values okay.



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So what we have to do is we have to avoid calling this copy constructor and how can we avoid calling



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this copy constructor by using passed by reference.



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Okay.



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So if you look here there is no need to pass by value.



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Okay.



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Vertical copy gastric but simply can pass biodefense because we are only accessing its properties.



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We are not doing anything extra.



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We are only accessing the properties of the student is so wide to call copy constructor.



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Okay so what will happen.



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We can also optimize it how we can meet.



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We can make it a constant reference.



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We have studied about this.



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Like if someone do this as soon as daughter age is minus one.



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So I want to avoid.



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I want to avoid this line.



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I want to avoid this a legal changes so to avoid this all legal changes begin but we can write constraint



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here.



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Okay.



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So what is happening here is



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the meaning of this line is very simple student constant reference variable S1 is that S1 so this is



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is the mean.



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This one from mean.



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Okay so this s is an offense variable the westward and constant.



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It is an offense variable to us and constraint so this time copy constructively logbook code.



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Okay so our inbuilt copy construct but also take argument in this session then we'll copy constructor



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also takes arguments in this section.



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But the problem with built copy constructor is then built a copy constructively make shallow copy but



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we want deep copy since we want the copy we have to write our own copy constructor okay.



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Okay sir.



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Okay.



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So I hope you understood this.



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Thank you.