#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
int main(void){
    double a,x;
    while(cin>>a,a!=-1){
        x=a*0.5;
        while(fabs(x*x*x-a)>=0.00001*a)x=x-(x*x*x-a)/(3*x*x);
        printf("%.6lf\n",x);
    }
    return 0;
}