#include <cstdio>

double abs(double n) {return n>0?n:-n;}

int main() {
  double q;
  while(scanf("%lf",&q), q>0) {
    double x = q/2;
    while (abs(x*x*x-q) >= 0.00001*q)
      x = x-(x*x*x-q)/(3*x*x);
    printf("%lf\n",x);
  }
}