#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0, i##_len = (n); i < i##_len; i++)
#define reps(i, s, n) for(ll i = (s), i##_len = (n); i < i##_len; i++)
#define rrep(i, n) for(ll i = (n) - 1; i >= 0; i--)
#define rreps(i, e, n) for(ll i = (n) - 1; i >= (e); i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((ll)(x).size())
#define len(x) ((ll)(x).length())

map<ll, ll> factorize2(ll n) {
    map<ll, ll> res;
    for (ll i = 2; (i * i) <= n; i++) {
        if (n % i) continue;
        res[i] = 0;
        while((n % i) == 0) {
            n /= i;
            res[i]++;
        }
    }
    if (n != 1) res[n] = 1;
    return res;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // ifstream in("input.txt");
    // cin.rdbuf(in.rdbuf());
    ll n;
    cin >> n;
    auto fac = factorize2(n);
    if (fac[3] > 0) {
        cout << 3 << endl;
    }
    else if (fac[2] >= 2) {
        cout << 4 << endl;
    }
    else {
        for(auto x : fac) {
            if ((x.first > 2) && (x.second > 0)) {
                cout << x.first << endl;
                break;
            }
        }
    }
    return 0;
}