#include <bits/stdc++.h>

using namespace std;

int main() {
    long long a;
    cin >> a;
    
    vector<int> answers(0);
    for (int n = 2; n < int(ceil(sqrt(float(a)))); ++n) {
        int m = int(ceil(log(float(a)) / log(float(n))));
        answers.push_back(n*m);
    }

    cout << *min_element(answers.begin(), answers.end()) << endl;
}