
import std.stdio, std.math;

double third_root(int n) {
  double x = n / 2.0;
  while ((pow(x, 3).abs - n) > 1e-6) {
    x = x - (pow(x, 3) - n) / (3 * x * x);
  }
  return x;
}

void main() {
  for(int n; readf("%d\n", &n), n != -1;)
    writefln("%2.6f", third_root(n));
}