#include <stdio.h>

int cancel_out( int arg_one, int arg_two, int *err)
{

  /* Arguments should not be equal */
  if ( arg_one == arg_two )
    {
      *err = 1;
      return 0;
    }
  else
    {
      *err = 0;
      return (arg_one - arg_two);
    }
}

main()
{
  int int1, int2, diff, err=0;
  int1=6;
  int2=7;

  diff = cancel_out(int1, int2, &err);

  if (err)
    {
      exit(1);
    }

  exit(0);
}