#include<iostream>
#include<iomanip>
#include<cstdlib>
#include<ctime>
#include<cmath>

using namespace std;

long long qmod(int a, int b, int p) {
    long long res = 1;

    long long term = a%p;

    while(b) {
        if(b&1){
            res = (res*term)%p;
        }
        
        term = (term*term)%p;
        b >>= 1;
    }

    return res;
}

bool is_prime(long long n) {   
    int i;
    for(i = 0; i < 100; ++i) {
        if(qmod(1+rand()%(n-1),n-1, n) != 1)
            break;
    }
    if(i < 100)
        return false;
    else 
        return true;
}

int main(void) {
    int n;
    while(cin >> n) {
        if(is_prime(n))
            cout << "yes" << endl;
        else 
            cout << "no" << endl;
    }
    return 0;
}