#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<cstdio>
#include<cmath>
using namespace std;
int main(){
long long int in;
while(cin>>in,in+1){
double x=in/2;
while(x*x*x-in>0.00001*in||x*x*x-in<-0.00001*in)
x-=(x*x*x-in)/(3*x*x);
if(in!=1)
printf("%.6f\n",x);
else
cout<<1<<endl;
}
}