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

int main() {
	long N, tmp, i;
	cin >> N;
	tmp = sqrt(N);
	for (i = 3; i <= tmp; ++i) {
		if (N % i == 0) break;
	}
	if (i == tmp + 1) {
		if (N % 2) cout << N;
		else cout << N / 2;
	}
	else cout << i;
}