import itertools

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

count=0
total=0
for a_perm in itertools.permutations(A):
    for b_perm in itertools.permutations(B):
        a_win=0
        for i in range(N):
            if a_perm[i] > b_perm[i]:
                a_win+=1
        if a_win>N/2:
            count+=1
        total+=1
print(count/total)