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

import itertools
ans = 0
for a in itertools.permutations(A, n):
    for b in itertools.permutations(B, n):
        w = 0
        for i in range(n):
            if a[i] > b[i]:
                w += 1
        if w > n-w:
            ans += 1
import math
ans /= math.factorial(n)**2
print(ans)