#include<bits/stdc++.h>
using namespace std;
bool isPrime(int x) {
    if (x <= 1) 
		return false;
    for (int i = 2; i * i <= x; ++i)
        if (x % i == 0) 
			return false;
    return true;
}
int main(){
	int n;
	while(cin >> n){
		if(isPrime(n))
			cout << "yes";
		else
			cout << "no";
	}
	return 0;
}