#include <cstdlib>
#include <iostream>

using namespace std;

constexpr int ZERO = int{};
constexpr int ONE  = sizeof(char);

constexpr int add(int x, int y) {
    return plus<>{}(x,y);
}

constexpr int succ(int x) {
    return add(x, ONE);
}

[[noreturn]] void no() {
    cout << "NO" << "\n";
    exit(ZERO);
}

int main() {
    int N; cin >> N;

    if(N == ONE) no();

    bool ans = true;
    for(int i = succ(ONE); i < N; i = succ(i)) {
        if(N%i == ZERO) {
            ans = false;
            break;
        }
    }

    cout << (ans ? "YES" : "NO") << "\n";

    return ZERO;
}