import math
from itertools import permutations
N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

# A はそのまま
# B の順番を変える（N!通り）

cnt = 0
for pat in permutations(B):
    win = 0
    lose = 0
    for i in range(N):
        # A[i] vs pat[i]
        if A[i] > pat[i]:
            win += 1
        else:
            lose += 1
    if win > lose:
        cnt += 1

ans = cnt/math.factorial(N)
print(ans)