Thanks, but I still get WA. Is this revised copy wrong as well?

#include <stdio.h>

long min, num, i;

int main() {
  scanf("%ld", &num);
  min = num - 1;
  if (num == 4) {
    min = 3;
  }

  if (num % 2 == 0) min = (num / 2) - 1;

  for (i = 3; i*i <= num; i++)
    if (num % i == 0)
      if ((i-1) < min) {
        min = i-1;
        break;
      }

  printf("%ld\n", min);

  return 0;
}