#include <iostream>
using namespace std;
bool is_prime(int n){
if(n <= 2) {
return false;
}
for(int i = 2;i<=n/i;i++) {
if(n % i == 0) return false;
}
return true;
}
int main() {
int n;
int cnt = 0;
while(cin >> n) {
if(n <= 0) break;
if(is_prime(n)){
cout << ++cnt << ": " << "yes"<<endl;
}else {
cout << ++cnt << ": " << "no" << endl;
}
}
}