#include "bits/stdc++.h"
using namespace std;

int main()
{
 double x;
 int q;
 while(1)
 {
   cin>>q;
   x=q/2;
  if(q==-1)
   break;
  while(fabs (x*x*x-q)>=0.00001*q)
   x=x-(x*x*x-q)/(3*x*x);
  cout<<setprecision(6)<<setiosflags(ios::fixed); 
	  cout<<x<<endl;
  
  
 
 }
return 0;
}