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

int main(){
	
	long long int q;
	double x;
	
	while(cin>>q){
		if(q!=-1){
			x=q/2;
			while(abs(pow(x,3)-q)>=0.00001*q){
				x=x-((pow(x,3)-q)/(3*pow(x,2)));
		}
			printf("%.6f\n",x);
	}
		else
			break;
	
	
}
}