#include <iostream>
using namespace std;
 
bool isPrime(int x){
	if (x < 2) return false;
	for (int i = 2; i*i <= x; i++){
		if (x%i == 0) return false;
	} return true;
}
 
int main() {
	int N;
	cin >> N;
	if (isPrime(N)) cout << "yes" << endl;
	else cout << "no" << endl;
	return 0;
}