import itertools
N = int(input())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
p = 1
for i in range(N):
    p /= (i+1)**2
ans = 0
for a in itertools.permutations(A):
    for b in itertools.permutations(B):
        tmp = 0
        for i in range(N):
            if a[i] > B[i]:
                tmp += 1
        if tmp > N-tmp:
            ans += 1
print(ans*p)