Swap values of two variable without using third.

//Program to swap values of two variable without using third.
#include<iostream.h>
#include<conio.h>
void main()
{
    clrscr();
    int a,b;
    cout<<"Enter first number: ";
    cin>>a;
    cout<<"Enter second number: ";
    cin>>b;
    a=a+b;
    b=a-b;
    a=a-b;
    cout<<"The first number is: "<<a<<endl;
    cout<<"The second number is: "<<b;
    getch();
}