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

typedef long long ll;

int main() {
	ll N;
	cin >> N;
	//cout << sqrt(N) << endl;
	for (ll i = 3; i <= sqrt(N); i++) {
		if (N%i == 0) {
			cout << i << endl;
			return 0;
		}
	}
	if(N%2==0 && (N/2)!=2) cout << N/2 << endl;
	else cout << N << endl;
}