#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <functional>
#include <iostream>
#include <map>
#include <set>
using namespace std;
typedef pair<int,int> P;
#define pu push
#define pb push_back
#define mp make_pair
#define eps 1e-7
#define INF 2000000000
int main()
{
	double x;
	int q;
	while(1)
	{
		cin >> q;
		if(q==-1)break;
		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;
}