#from __future__ import annotations
from typing import List,Union
import sys
input = sys.stdin.readline
# from collections import defaultdict,deque
from itertools import permutations,combinations
# from bisect import bisect_left,bisect_right
# import heapq
# sys.setrecursionlimit(10**5)

def main():
    N = int(input())
    A = list(map(int,input().split()))
    B = list(map(int,input().split()))

    total = 0
    wins = 0

    for a in permutations(A):
        for b in permutations(B):
            total += 1
            win = 0
            lose = 0
            for x,y in zip(a,b):
                if x > y: win += 1
                if x < y: lose += 1
            if win > lose: wins += 1

    print(wins/total)


if __name__ == '__main__':
    main()