#include <stdio.h>double zenka(double q){    double x=q/2;        while(x*x*x-q>=0.00001*q || x*x*x-q<=-0.00001*q)    {        x=x-((x*x*x)-q)/(3*x*x);    }        return x;}int main(void){    int q;        while(1)    {        scanf("%d",&q);        if(q==-1) break;        else        {            printf("%.7f\n",zenka(q));        }    }        return 0;}
