import bisect,collections,copy,itertools,math,string
import sys
def I(): return int(sys.stdin.readline().rstrip())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def main():
    n = I()
    a = LI()
    b = LI()
    a_per = list(itertools.permutations(a))
    b_per = list(itertools.permutations(b))
    all_game = math.factorial(n)**2
    cnt_game = 0
    for acards in a_per:
        for bcards in b_per:
            acnt = 0
            for acard, bcard in zip(acards, bcards):
                if acard>bcard:
                    acnt+=1
            bcnt = n-acnt
            if acnt>bcnt:
                cnt_game+=1
    ans = cnt_game/all_game
    print(ans)

main()