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

class Program
{
    void Solve()
    {
        double ans = 0;
        int N = reader.Int();
        var A = reader.IntArray(N).OrderBy(x => x).ToArray();
        var B = reader.IntArray(N);


        do
        {
            double wins = 0, total = 0;
            Array.Sort(B);
            do
            {
                total++;
                int balance = Enu.Range(0, N).Sum(i => Math.Sign(A[i] - B[i]));
                if (balance > 0) wins++;
            } while (NextPermutation(B));

            double prob = wins / total;
            ans = Math.Max(ans, prob);

        } while (NextPermutation(A));

        Console.WriteLine(ans);
    }

    static bool NextPermutation<T>(T[] a)
    {
        Comparer<T> comp = Comparer<T>.Default;
        for (int i = a.Length - 2; i >= 0; i--)
        {
            if (comp.Compare(a[i], a[i + 1]) < 0)
            {
                int j = a.Length - 1;
                while (comp.Compare(a[i], a[j]) >= 0) { j--; }
                T tmp = a[i]; a[i] = a[j]; a[j] = tmp;
                Array.Reverse(a, i + 1, a.Length - 1 - i);
                return true;
            }
        }
        return false;
    }


    static void Main() { new Program().Solve(); }
    Reader reader = new Reader(Console.In);
    class Reader
    {
        private readonly TextReader reader;
        private readonly char[] separator = { ' ' };
        private readonly StringSplitOptions removeOp = StringSplitOptions.RemoveEmptyEntries;
        private string[] A = new string[0];
        private int i;

        public Reader(TextReader r) { reader = r; }
        public bool HasNext() { return Enqueue(); }
        public string String() { return Dequeue(); }
        public int Int() { return int.Parse(Dequeue()); }
        public long Long() { return long.Parse(Dequeue()); }
        public double Double() { return double.Parse(Dequeue()); }
        public int[] IntLine() { var s = Line(); return s == "" ? new int[0] : Array.ConvertAll(Split(s), int.Parse); }
        public int[] IntArray(int N) { return Enumerable.Range(0, N).Select(i => Int()).ToArray(); }
        public int[][] IntGrid(int H) { return Enumerable.Range(0, H).Select(i => IntLine()).ToArray(); }
        public string[] StringArray(int N) { return Enumerable.Range(0, N).Select(i => Line()).ToArray(); }
        public string Line() { return reader.ReadLine().Trim(); }
        private string[] Split(string s) { return s.Split(separator, removeOp); }
        private bool Enqueue()
        {
            if (i < A.Length) return true;
            string line = reader.ReadLine();
            if (line == null) return false;
            if (line == "") return Enqueue();
            A = Split(line);
            i = 0;
            return true;
        }
        private string Dequeue() { Enqueue(); return A[i++]; }
    }
}