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

n = math.factorial(N)**2
c = 0
for a in itertools.permutations(A):
    for b in itertools.permutations(B):
        aw, bw = 0, 0
        for j, k in zip(a,b):
            if j > k:
                aw += 1
            else:
                bw += 1
        if aw > bw:
            c += 1
        
print(c/n)