#include <iostream>

bool is_prime(int n)
{
   if(n < 2) return false;
   for(int i = 2; n >= i*i; i++)
      if((n % i) == 0) return false;
   return true;
}

int main()
{
   int x = 900;
   if(is_prime(x))
      std::cout << x << " is prime.\n";
   else std::cout << x << " is not prime.\n";
}