import itertools
import math
N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
ans = 0
for comb_a in itertools.permutations(range(N)):
    for comb_b in itertools.permutations(range(N)):
        a_win, b_win = 0, 0
        for i in range(N):
            if A[comb_a[i]] > B[comb_b[i]]:
                a_win += 1
            elif A[comb_a[i]] < B[comb_b[i]]:
                b_win += 1
        if a_win > b_win: ans += 1
print(ans/math.factorial(N)**2)