#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
	ll n;
	cin >> n;
	if (n % 3 == 0) {
		cout << 3 << endl;
		return 0;
	}
	else if (n % 4 == 0) {
		cout << 4 << endl;
		return 0;
	}
	if (n % 2 == 0) {
		n /= 2;
	}
	for (ll i = 3;i*i <= n;i++) {
		if (n%i == 0) {
			cout << i << endl;
			return 0;
		}
	}
	cout << n << endl;

	return 0;
}