Swapping without temp variable

#include<stdio.h>

main()
{
  int num1,num2;

  printf("Enter number 1 :  ");
  scanf("%d",&num1);

  printf("Enter number 2 :  ");
  scanf("%d",&num2);

  printf("Before swapping\n");
  printf("number 1 is %d and number 2 is %d\n",num1,num2);

  num1=num1+num2;
  num2=num1-num2;
  num1=num1-num2;

  printf("After swapping \n");
  printf("number 1 is %d and number 2 is %d\n",num1,num2);
}