C++ :

#include <iostream>
#include <stdio.h>
#include <string.h>

using namespace std;

int isprime[10005];
int main() {
	//freopen("totalfrank.in", "r", stdin);
	//freopen("totalfrank.out", "w", stdout);
	
  memset(isprime, true, sizeof(isprime));
  isprime[1] = 0;
  isprime[0] = 0;
  for (int i = 2; i <= 100; i++) {
    if (isprime[i])
      for (int j = 2; i * j <= 10000; j++) {
        isprime[i * j] = 0;
      }
  }
  int q;
  while (~scanf("%d", &q)) {
    if (isprime[q]) {
      puts("YES");
    } else {
      puts("NO");
    }
  }
  return 0;
}