#include <iostream>

using namespace std;

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