#include <iostream>

using namespace std;

unsigned long long func(unsigned long long n) {
    for (int i = 3; i * i <= n; i += 2) {
        if (n % i == 0) {
            return i;
        }
    }
    return n;
}

int main() {

    ios::sync_with_stdio(false);
    cin.tie(0);

    unsigned long long n;
    cin >> n;
    cout << func(n) << endl;
    return 0;
}