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