N = int(input())

from itertools import permutations

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

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

W = 0

S = 0

for i in permutations(range(N), r=N):
    
    for j in permutations(range(N), r=N):
        
        if sum([1 if A[i[k]] > B[j[k]] else 0 for k in range(N)]) > sum([1 if A[i[k]] < B[j[k]] else 0 for k in range(N)]):
            
            W += 1
            
        S += 1
        
        
print(W / S)