#include "bits/stdc++.h"
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;
	else cout << N << endl;
	return 0;
}