#include <bits/stdc++.h>
using namespace std;
bool isPrime(int num) 
{
    if (num < 2) 
        return false;
    for (int i = 2; i * i <= num; i++) 
        if (num % i == 0) {
            return false;
    return true;
}
int main() {
    int num;
    cin >> num;
    if (isPrime(num)) 
        cout << num << " 是质数。" ;
    else
        cout << num << " 不是质数。";
    }
    return 0;
}