#include <iostream>
#include <cstdint>

using namespace std;

uint64_t func(uint64_t n) {
    if (n % 3 == 0) {
        return 3;
    }
    if (n % 4 == 0) {
        return 4;
    }
    if (n % 2 == 0) {
        n /= 2;
    }
    for (uint64_t i = 5; i * i <= n; i += 2) {
        if (n % i == 0) {
            return i;
        }
    }
    return n;
}

int main() {

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

    uint64_t n;
    cin >> n;
    cout << func(n) << endl;
    return 0;
}