#include <iostream>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <algorithm>
#include <functional>

using namespace std;

int main()
{
	while ( true )
	{
		int q;
		cin >> q;
		
		if ( q == -1 )
		{
			break;
		}

		double x = q / 2.0;

		while ( q * 0.00001 < abs( pow( x, 3 ) - q ) )
		{
			x -= ( ( pow( x, 3 ) - q ) / ( 3 * pow( x, 2 ) ) );
		}

		printf("%.6lf\n", x );
	}

	return 0;
}