Write a c program to swap two numbers without using third variable ?

Write a c program to swap two numbers without using third variable ?

#include<stdio.h>
#include<conio.h>
int main() 
{
   int x, y;
   printf("\nEnter value for num1 & num2 : ");
   scanf("%d %d", &x, &y);
   x = x + y;
   y = x - x;
   x = x - y;
   printf("\nAfter swapping value of a : %d", x);
   printf("\nAfter swapping value of b : %d", y);
   return (0);
}

Output

Enter value for num1 & num2 : 20 10
After swapping value of a : 10

After swapping value of b : 20