#include<cstdio>
#include<iostream>
#include<string>
#include<cmath>
#include<vector>
#include<stack>
#include<queue>
#include<algorithm>
#include<complex>
using namespace std ;
typedef vector<int> vi ;
typedef vector<vi> vvi ;
typedef vector<string> vs ;
typedef pair<int, int> pii; 
typedef long long ll ;

#define loop(i,a,b) for(int i = a ; i < b ; i ++)
#define rep(i,a) loop(i,0,a)
#define all(a) (a).begin(),(a).end()


int main(void){
  double buf;
  while(cin>>buf,buf>0){
    double x = buf / 2;
    while(1){
      x = x - (x*x*x-buf)/(3*x*x);
      if(abs(x*x*x-buf) < 0.00001*buf)break;
    }
    printf("%6f\n",x);
  }
}