fibonacci (non-recursive)

#include <stdio.h>

long int fib(int n)
{
   long int f1 = 0, f2 = 1;
   int i;
   for (i = 1; i <= n; i += 1)
   {
      f2 = f1+f2;
      f1 = f2-f1;
   }
   return f1;
}

int main(void)
{
   int n;
   int qualifier = 1;
   while (qualifier == 1 || qualifier == 0)
   {
      qualifier = scanf("%d", &n);
      if (qualifier == 1 && n >= 0)
         {
            printf("%ld\n", fib(n));
         }
      if (qualifier == 1 && n < 0)
         {
            printf("wrong type\n");
         }
   }
   return 0;

}