#include <stdio.h>
#include <stdlib.h>

int isprime(int n)
{
  if (n <= 1)
    return 0;

  for (int i = 2; i <= n / 2; i++)
    if (n % i == 0)
      return 0;

  return 1;
}

int main(int argc, char *argv[])
{
  int n = 7;

  printf("%d is %s prime\n", n, isprime(n) ? "a" : "not a");

  return 0;
}