Subtraction without '-' operator

source code:

#include<stdio.h>

   int main()

  {

    int a,b;

    int sum;

    printf("Enter any two integers:/n ");

    scanf("%d%d",&a,&b);

       sum = a + ~b + 1;

    printf("Difference of two integers: %d",sum);

       getch();

       return 0;

  }