//C++14 (Clang 3.8.0)

#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <string>
#include <climits>
using namespace std;
typedef long long ll;
typedef pair<long long,long long> P;

int main(){
  while(1){
    double n;
    cin>>n;
    if(n==-1.0)break;
    double x=n/2;
    while(1){
      if(abs(x*x*x-n)<0.00001*n)break;
      x=(x-((x*x*x)-n)/(3*x*x));
    }
    printf("%.6lf\n",x);

  }

}

