from itertools import permutations


n=int(input())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
cnt=0
win=0


for i in permutations(A,n):
    cnt+=1
    w=0
    for x,y in zip(i,B):
        if x>y:
            w+=1
        elif y>x:
            w-=1
    if w>0:
        win+=1

print(win/cnt)