#include <iostream>

using namespace std;

int main() {
    long long n;
    cin >> n;
    for (long long i = 3; i * i <= n; i++) {
        if (n % i == 0) {
            cout << i << endl;
            return 0;
        }
    }

    if (n % 2 == 0 && n / 2 > 2)cout << n / 2 << endl;
    else cout << n << endl;
    return 0;
}