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

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

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

	cout << n << endl;

	return 0;
}