#include <vector>
#include <iostream>
#include <string>
#include <sstream>
#include <algorithm>
#include <utility>
#include <map>
#include <cmath>

using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;

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