import itertools
import math
N = int(input())
A = [int(i) for i in input().split()]
B = [int(i) for i in input().split()]

ans = 0
for a in itertools.permutations(A):
    for b in itertools.permutations(B):
        c = sum(1 if a[i] > b[i] else (-1 if a[i] < b[i] else 0)
                for i in range(N))
        if c > 0:
            ans += 1

print(ans/math.factorial(N)**2)