#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);
const double EPS = 1e-12;
const long long INF = 1LL<<60;

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  long long a;
  cin >> a;

  long long ret = INF;

  for (int n = 2; n < 100000; n++) {
    long long m = (log(a) / log(n)) + (1 - EPS);
    ret = min(ret, n * m);
  }
  
  cout << ret << endl;
  
  return 0;
}