#include <bits/stdc++.h>
#include <cmath>
using namespace std;

int main(){
    int x;
    cin >> x;
    if(x < 2) cout << "no" << endl;
    else {
        for(int i = 2 ; i<=sqrt(x);i++){
            if(x % i == 0) {
                cout << "no" << endl;
                return 0;
            }
        }
        cout << "yes" << endl;
    }
}