#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 && N > 4){
		cout << N / 2 << endl;
	} else {
		cout << N << endl;
	}
}