from itertools import *
n=int(input())
g=0
w=0
a=list(map(int,input().split()))
b=list(map(int,input().split()))
for j in permutations(a):
    for k in permutations(b):
        g+=1
        aa=0
        bb=0
        for i in range(n):
            if j[i]>k[i]:
                aa+=1
            else:
                bb+=1
        if aa>bb:
            w+=1
print(w/g)