#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;
}