Swapping without using 3rd(temp) variable.........

#include<iostream.h>
#include<conio.h>
void main()
{

int a,b;
clrscr();
cout<<"ENTER TWO NUMBERS\n";
cin>>a>>b;
cout<<"a="<<a<<"\n"<<"b="<<b<<endl;
a=a+b;
b=a-b;
a=a-b;
cout<<"AFTER SWAPPING\n";
cout<<"a="<<a<<"\n"<<"b="<<b;
getch();
}