using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;
using System.Globalization;

class Program
{
    static int NN => int.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();

    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NN;
        if (c == 0)
        {
            WriteLine("0.000");
            return;
        }
        var ng = 5001L;
        var ok = 0L;
        while (ng - ok > 1)
        {
            var d = (ok + ng) / 2;
            var f = d * d * d * d * d + d * 1_000_000_000_000 - c * 1_000_000_000_000_000;
            if (f <= 0) ok = d;
            else ng = d;
        }
        WriteLine(((decimal)ok / 1000).ToString("0.000"));
    }
}