#include <iostream>
using namespace std;
int main() {
    long long A; cin >> A;
    long long ans = 120;
    for (long long n = 2; n < ans; n++) {
        long long m = 1, p = n;
        while (p < A) { p *= n; m++; }
        ans = min(ans, n * m);
    }
    cout << ans << endl;
}