#include <iostream>
#include <string>

using namespace std;

typedef unsigned long long uint64;

int main() {
    uint64 n;
    uint64 i;
    cin >> n;

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

    return 0;
}