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

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 = NList;
        var (h, w) = (c[0], c[1]);
        var p = double.Parse(ReadLine());
        if (h > w) (h, w) = (w, h);
        if (w == 1) WriteLine(p);
        else if (h == 1) WriteLine(2 * p * p + (w - 2) * p * p * p);
        else WriteLine(4 * p * p * p + (h + w - 4) * 2 * p * p * p * p + (h - 2) * (w - 2) * p * p * p * p * p);
    }
}