#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

inline int ceillog(ll x, int base) {
  int ans = 0;
  while (x > 0) {
    x /= base;
    ans++;
  }
  return ans;
}

int main() {
  ll a;
  cin >> a;
  ll ans = a;
  for (ll b = 2; b <= ans; b++) {
    int p = ceillog(a, b);
    Debug(a, b, p, b * p, ans);
    ans = min(ans, (ll) b * p);
  }
  cout << ans << endl;
  return 0;
}