#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

ll solve(ll n){
    if(n % 3 == 0) return 3;
    if(n % 4 == 0) return 4;
    for(ll i = 5; i*i <= n; i += 2){
        if(n % i == 0) return i;
    }
    return n;
}

int main(){
    ll n; cin >> n;
    cout << solve(n) << endl;
}