from itertools import permutations

N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
al, wi = 0, 0
for v1 in permutations(range(N), N):
    for v2 in permutations(range(N), N):
        ss = 0
        al += 1
        for i in range(N):
            if A[v1[i]]>B[v2[i]]:
                ss += 1
        if ss>N-ss:
            wi+=1
print(wi/al)