C++ Program .Write a program swap (exchange ) two number withut using thard variable .

#include<stdio.h>
#include<conio.h>
void main()
{
int a,b;
clrscr();
printf("\n enter the value of a");
scanf("\n %d",&a);
printf("\n enter the value of b");
scanf("\n %d",&b);
a=a+b;
b=a-b;
a=a-b;
printf("\n swapped value is %d",a);
printf("\n swapped value is  %d",b);
getch();
}