#include <iostream>
using namespace std;
 
// 소수 판별 함수 (에라토스테네스의 체 방식 X, 일반적인 방식)
bool isPrime(int num) {
    if (num < 2) return false; // 2 미만의 숫자는 소수가 아님
    if (num == 2) return true; // 2는 유일한 짝수 소수
    if (num % 2 == 0) return false; // 짝수는 소수가 아님 (2 제외)
 
    // 3부터 √num까지 홀수만 검사 (최적화)
    for (int i = 3; i * i <= num; i += 2) {
        if (num % i == 0) return false;
    }
 
    return true;
}
 
int main() {
    int N;
    cin >> N;
 
    if (isPrime(N))
        cout << "YES" << endl;
    else
        cout << "NO" << endl;
 
    return 0;
}

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32