#include <string>
#include <iostream>
#include <cmath>
using namespace std;

typedef long long int ll;

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

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

	cout << n << endl;

	return 0;
}