#include <iostream>
#include <algorithm>
#include <cassert>
#include <cctype>
#include <complex>
#include <cstdio>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
using namespace std;

double q;

int main(){
	while(cin>>q){
		if(q==-1)return 0;
		double x=q/2;
		while(fabs(x*x*x-q)>=q*1e-5)x-=(x*x*x-q)/3/x/x;
		printf("%.6f\n",x);
	}
}