素数判定

//素数判定

#include <iostream>
#include <cstdio>
#include <cmath>

using namespace std;

bool Judge(int n) {
  if (n < 2) {
    return false;
  }
  int bound = sqrt(n);
  for (int i = 2; i <= bound; ++i) {
    if (n % i == 0) {
      return false;
    }
  }
  return true;
}

int main() {
  int n;
  while (scanf("%d", &n) != EOF) {
    if (Judge(n)) {
      printf("yes\n");
    } else {
      printf("no\n");
    }
  }
  return 0;
}