#include <iostream> //designed by hu 2025-10 using namespace std; int isPrime(int n) { if(n==1) return 0; for(int i=2;i*i<=n;i++) { if(n%i==0) { return 0; } } return 1; } int main(){ int num; cin>>num; if ( isPrime(num)) cout<<"YES"; else cout<< "NO"; return 0; }