#include<iostream>
#include <cmath>
#include <iomanip>

using namespace std;

int main()
{
  double x,q;
  for(;cin>>q,q!=-1;)
    {
      x=q/2;
      for(;abs(x*x*x-q)>=0.00001*q;)
	{
	  x=x-((x*x*x-q)/(3*x*x)); 
	}
      cout<<setprecision(7)<<x<<endl;
      
    }
}