from itertools import combinations, permutations, product
from math import factorial


n=int(input())
al=list(map(int,input().split()))
bl=list(map(int,input().split()))

cnt=0
for ao in permutations(al):
    for bo in permutations(bl):
        win=0
        lose=0
        for i in range(n):
            if ao[i]>bo[i]:
                win+=1
            elif ao[i]<bo[i]:
                lose+=1
        if win>lose:
            cnt+=1

allpattern=factorial(n)**2
print(cnt/allpattern)