#include <bits/stdc++.h>

using namespace std;

using ll = long long;

int main()
{
    ll n; cin >> n;

    for (ll i = 3; i * i <= n; ++i) {
        if (n % i == 0) {
            cout << i << endl;
            return 0;
        }
    }

    ll a = n;

    if (a % 2 == 0 && a > 4) a /= 2;

    cout << a << endl;
}