#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using P = pair<int,int>;

int main() {
  ll a;
  cin >> a;
  ll ans = 1e18;
  for (ll n = 2; n < 150; ++n) {
    ll m = 0;
    ll p = 1;
    while (p < a) {
      p *= n;
      ++m;
    }
    ans = min(ans, n * m);
  }
  cout << ans << endl;
  return 0;
}