#include <iostream>
#include <cmath>
#include <cstdio>
#include
using namespace std;

int main(){
	int q;
	while(cin>>q&&q!=-1){
		double x=q/2.0;
		while(fabs(x*x*x-q)>=0.00001*q)x-=(x*x*x-q)/(3*x*x);
		printf("%.6f\n", x);
	} 
	return 0;
}