#include <bits/stdc++.h>

using namespace std;

using ll = long long;

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

    for (int i = 3; pow(i, 2) <= n; ++i) {
        if (!(n % i)) {
            cout << i << endl;
            return 0;
        }
    }

    cout << n << endl;
}