#include <bits/stdc++.h> using namespace std; typedef long long int ll; typedef pair<ll, ll> P; typedef vector<ll> VI; typedef vector<VI> VVI; const ll MOD = 1000000007; const ll INF = 1e18; #define REP(i, n) for(int i = 0; i < n; i++) #define ALL(v) v.begin(), v.end() int main(){ ll a; cin >> a; ll ans=INF; for(int k=2;k<=5;k++){ int c=0; for(ll i=1;i<a;i*=k){ c++; } ans=min(ans,(ll)c*k); } cout << ans << endl; return 0; }