#include<iostream>
#include<math.h>
#include<vector>
#include<algorithm>
#include<cstdio>
using namespace std;
int main(void)
{
    double q, x, eq;
    while(scanf("%lf",&q),q>0)
    {
        x = q/2;
        eq = q*0.00001;
        while(fabs(x*x*x-q) >= eq)
            x -= (x*x*x-q)/(3*x*x);
        printf("%f\n", x);
    }
    return 0;
}
