#include <bits/stdc++.h>
#define PB push_back
#define MP make_pair
#define REP(i,n) for (int i=0;i<(n);i++)
#define ALL(a) (a).begin(),(a).end()
#define INF 1000000001
#define MOD 10000
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
const ull B=100000007;
int main(){
      int q;
      while(cin>>q&&q!=-1){
            double x=(double)q/2.0;
            while(1){
                  if(0.00001*q>abs(x*x*x-q))break;
                  x=x-((x*x*x-q)/(3.0*x*x));
            }
            printf("%.10f\n",x);
      }
}