Swap 2 numbers without using 3rd variable

#include<stdio.h>
main()
{
int a,b;

printf("nEnter value for num1 & num2 : ");
scanf("%d %d",&a,&b);
a=a+b;
b=a-b;
a=a-b;
printf("nAfter swapping value of a : %d",a);
printf("nAfter swapping value of b : %d",b);
}