using System;
using System.Collections.Generic;
using System.Linq;
public class Program{
    public static void Main(){
        var n = int.Parse(Console.ReadLine());
        var a = new int[n];
        var b = new int[n];
        var A = Console.ReadLine().Split(' ');
        var B = Console.ReadLine().Split(' ');
        int i;
        for(i=0;i<n;i++){
            a[i] = int.Parse(A[i]);
            b[i] = int.Parse(B[i]);
        }
        Array.Sort(a);
        Array.Sort(b);
        var AA = AllPermutation(a);
        var BB = AllPermutation(b);
        double win = 0;
        foreach(var aa in AA){
            foreach(var bb in BB){
                var awin = 0;
                var bwin = 0;
                for(i=0;i<n;i++){
                    if(aa[i]>bb[i]){
                        awin++;
                    }
                    else if(aa[i]<bb[i]){
                        bwin++;
                    }
                }
                if(awin>bwin){
                    win++;
                }
            }
        }
        Console.WriteLine(win/Math.Pow(AA.Count,2));
    }
    static List<T[]> AllPermutation<T>(params T[] array) where T : IComparable
    {
        var a = new List<T>(array).ToArray();
        var res = new List<T[]>();
        res.Add(new List<T>(a).ToArray());
        var n = a.Length;
        var next = true;
        while (next)
        {
            next = false;
    
            // 1
            int i;
            for (i = n - 2; i >= 0; i--)
            {
                if (a[i].CompareTo(a[i + 1]) < 0) break;
            }
            // 2
            if (i < 0) break;
    
            // 3
            var j = n;
            do
            {
                j--;
            } while (a[i].CompareTo(a[j]) > 0);
    
            if (a[i].CompareTo(a[j]) < 0)
            {
                // 4
                var tmp = a[i];
                a[i] = a[j];
                a[j] = tmp;
                Array.Reverse(a, i + 1, n - i - 1);
                res.Add(new List<T>(a).ToArray());
                next = true;
            }
        }
        return res;
    }
}