//土尔逊Torson 编写于2023/5/08
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cstdio>
#include <math.h>

using namespace std;

bool Judge(int x) {              //判断是否为质数(素数)
	if (x < 2) {                 //小于2必定不是
		return false;
	}
	int bound = sqrt(x);         //确定判定上界
	for (int i = 2; i <= bound; ++i) {
		if (x%i == 0) {
			return false;
		}
	}
	return true;
}

int main() {
	int n;
	while (scanf("%d", &n) != EOF) {
		if (Judge(n)) {
			printf("yes\n");
		}
		else {
			printf("no\n");
		}
	}
	system("pause");
	return EXIT_SUCCESS;
}
// 64 位输出请用 printf("%lld")