#include <iostream>

using lint = long long;

void solve() {
    lint x;
    std::cin >> x;

    lint ans = 120;
    for (lint n = 2; n <= x && n < ans; ++n) {
        lint m = 1, y = n;
        while (y < x && n * m < ans) {
            ++m;
            y *= n;
        }
        ans = std::min(ans, n * m);
    }

    std::cout << ans << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}