#include<iostream>
using namespace std;
double r3(double x, double s, double d)
{
       if(d-s<=0.0001) return d;
       else 
       { double m=(s+d)/2;
         if(m*m*m<x) return r3(x,m,d);
            else return r3(x,s,m);  
       } 
}

int main()
{ double x;
  cin>>x;
  if(x>0) if(x<1) cout<<r3(x,0,1);
          else  cout<<r3(x,0,x);
  else if(x>-1) cout<<r3(x,-1,0);
       else cout<<r3(x,x,0);
  system("pause");
  return 0;
}