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#include <bits/stdc++.h>
using namespace std;
int main() {
int num;
bool prime = true;
cin>>num;
if(num<=1){
    prime = false;
}else {
    for(int i = 2; i * i <= num; ++i){
        if(num % i == 0){
            prime = false;
        }
    }
}
if(prime){
    cout<<"YES";
}else {
cout<<"NO";
}
}