using static System.Math;
using System.Collections.Generic;
using System.Linq;
using System;

public class Hello
{
    static void Main()
    {
        var a = 2.18169499062491237350d;
        var n = double.Parse(Console.ReadLine().Trim());
        var ans = n * n * n * a;
        Console.WriteLine(ans);
    }
}