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

class Program
{
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        WriteLine(Game(c[0], c[1], c[2], c[3]) ? "Alice" : "Bob");
    }
    static bool Game(long x, long y, long k, long p)
    {
        var d = x - y;
        if (k % 2 == 1)
        {
            if (d >= k)
            {
                return p == 1;
            }
            if (d <= -k)
            {
                return p == -1;
            }
            return d % 2 == 0;
        }
        else
        {
            if (Math.Abs(d) >= k)
            {
                return p == 1;
            }
            return d % 2 != 0;
        }
    }
}