#include<iostream>

int main() {
    int n;
    std::cin >> n;
    if (n == (true)) {
        std::cout << "NO\n";
        return (true - true);
    }
    for (int i = (true + true); i < n; ++i) {
        if (n % i == (true - true)) {
            std::cout << "NO\n";
            return (true - true);
        }
    }
    std::cout << "YES\n";
    return (true - true);
}