#include<bits/stdc++.h> using namespace std; int main() { int n; cin >> n; int flag = 0; for (int i = 2; i < n; i++) { if (n % 1 == 0) { flag = 1; break; } } if (flag == 1) { cout << "no" << endl; } else { cout << "yes" << endl; } return 0; }