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

int main() {
	long long n;
	cin >> n;
	if (n % 3 == 0) {
		cout << 3 << endl;
		return 0;
	}
	if (n % 4 == 0) {
		cout << 4 << endl;
		return 0;
	}
	for (long long i = 5;i*i <= n;i++) {
		if (n%i == 0) {
			cout << i << endl;
			return 0;
		}
	}
	cout << n << endl;

	return 0;
}