using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace Competitive
{
    internal class Solution
    {
        public int N;
        public int[] A, B;
        public int count;
        public int win;
        public List<int[]> orders;
        public void Run()
        {
            N = Input.ReadInt();
            A = Input.ReadIntArray();
            B = Input.ReadIntArray();

            orders = new List<int[]>();
            count = 0;
            win = 0;
            var pm = new Permutation(N, Process);
            pm.DFSRun();

            for (int i = 0; i < orders.Count; i++)
                for(int j = 0; j < orders.Count; j++)
                {
                    int w = 0;
                    int l = 0;
                    for (int k = 0; k < N; k++)
                    {
                        if (A[orders[i][k]] > B[orders[j][k]]) w++;
                        else l++;
                    }

                    if (w > l) win++;
                    count++;
                }

            Console.WriteLine(((double)win)/ count);

        }

        public void Process(int[] order)
        {
            orders.Add((int[])order.Clone());
        }

    }

    // libs ----------
    // Permutationを全通り列挙
    class Permutation
    {
        public int N;
        public bool[] F;
        public int[] V;
        public Action<int[]> Process;

        public Permutation(int N, Action<int[]> process)
        {
            this.N = N;
            Process = process;
        }

        public void DFSRun()
        {
            F = new bool[N];
            V = new int[N];
            DFS(0);
        }

        private void DFS(int i)
        {
            if (i == N)
            {
                Process(V);
            }
            else
            {
                for (int k = 0; k < N; k++)
                    if (!F[k])
                    {
                        F[k] = true;
                        V[i] = k;
                        DFS(i + 1);
                        F[k] = false;
                    }
            }
        }

    }

    // common ----------

    internal static class Input
    {
        public static string ReadString()
        {
            string line = Console.ReadLine();
            return line;
        }

        public static int ReadInt()
        {
            string line = Console.ReadLine();
            return int.Parse(line);
        }

        public static int[] ReadIntArray()
        {
            string line = Console.ReadLine();
            return line.Split(' ').Select(int.Parse).ToArray();            
        }

        public static long ReadLong()
        {
            string line = Console.ReadLine();
            return long.Parse(line);
        }

        public static long[] ReadLongArray()
        {
            string line = Console.ReadLine();
            return line.Split(' ').Select(long.Parse).ToArray();
        }

        public static double[] ReadDoubleArray()
        {
            string line = Console.ReadLine();
            return line.Split(' ').Select(double.Parse).ToArray();
        }
    }
    
    internal class Program
    {
        public static void Main(string[] args)
        {
            var s = new Solution();
            s.Run();
        }
    }
}