#include <iostream>
#include <cstdio>
#include <vector>
#include <map>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <functional>
#define _USE_MATH_DEFINES
#include <math.h>
#include <string.h>

using namespace std;
static const double EPS = 1e-6;


void solve()
{
	int q;
	while (cin >> q, q != -1)
	{
		double left = 0.0;
		double right = 1 << 24;
		for (int i = 0; i < 100; ++i)
		{
			double mid = (left + right) / 2;
			if (q - mid * mid * mid > EPS)
			{
				left = mid;
			}
			else
			{
				right = mid - 0.0001;
			}
		}
		printf("%.8f\n", left);
	}
}

int main()
{
	solve();
	return(0);
}