#include <bits/stdc++.h>

namespace solver{
  void solve(){
    int64_t A; std::cin >> A;

    int64_t ans = A;

    for(int N = 1; N <= 300; ++N){
      int64_t k = 1;
      for(int M = 1; M <= 100; ++M){

        if(__builtin_smulll_overflow(k, N, (long long int*)&k)){
          break;
        }

        if(k >= A){
          ans = std::min<int64_t>(ans, N * M);
        }
      }
    }

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

int main(){
  solver::solve();
  return 0;
}