using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using System.Diagnostics;
using Enu = System.Linq.Enumerable;

class Program
{
    static readonly int TimeLimit = 2000;
    static Random random = new Random(0);

    public void Solve()
    {
        int N = Reader.Int();
        double PA = Reader.Double(), PB = Reader.Double();
        int[] A = Reader.IntArray(N), B = Reader.IntArray(N);
        Array.Sort(A); Array.Sort(B);
        double wins = 0, total = 0;
        var sw = Stopwatch.StartNew();

        while (sw.ElapsedMilliseconds < TimeLimit)
        {
            total++;
            if (Win(A.ToList(), B.ToList(), PA, PB)) wins++;
        }

        Console.WriteLine(wins / total);
    }

    private bool Win(List<int> A, List<int> B, double PA, double PB)
    {
        Func<int, double, int> Select = (N, p) =>
        {
            if (N == 1 || random.NextDouble() < p) return 0;
            return random.Next(1, N);
        };
        int ptA = 0, ptB = 0;
        for (int N = A.Count; N >= 1; N--)
        {
            int ai = Select(N, PA), bi = Select(N, PB);
            if (A[ai] > B[bi]) ptA += A[ai] + B[bi];
            else ptB += A[ai] + B[bi];
            A.RemoveAt(ai); B.RemoveAt(bi);
        }
        return ptA > ptB;
    }
}


class Entry { static void Main() { new Program().Solve(); } }
class Reader
{
    private static TextReader reader = Console.In;
    private static readonly char[] separator = { ' ' };
    private static readonly StringSplitOptions op = StringSplitOptions.RemoveEmptyEntries;
    private static string[] A = new string[0];
    private static int i;
    private static void Init() { A = new string[0]; }
    public static void Set(TextReader r) { reader = r; Init(); }
    public static void Set(string file) { reader = new StreamReader(file); Init(); }
    public static bool HasNext() { return CheckNext(); }
    public static string String() { return Next(); }
    public static int Int() { return int.Parse(Next()); }
    public static long Long() { return long.Parse(Next()); }
    public static double Double() { return double.Parse(Next()); }
    public static int[] IntLine() { return Array.ConvertAll(Split(Line()), int.Parse); }
    public static int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
    public static int[][] IntTable(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
    public static string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Line()).ToArray(); }
    public static string Line() { return reader.ReadLine().Trim(); }
    private static string[] Split(string s) { return s.Split(separator, op); }
    private static string Next() { CheckNext(); return A[i++]; }
    private static bool CheckNext()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return CheckNext();
        A = Split(line);
        i = 0;
        return true;
    }
}