import sys
from itertools import permutations

sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline
f_inf = float('inf')
mod = 10 ** 9 + 7


def resolve():
    n = int(input())
    A = list(map(int, input().split()))
    B = list(map(int, input().split()))

    win = 0
    total = 0
    for pattern_A in permutations(A):
        for pattern_B in permutations(B):
            total += 1
            cnt = 0
            for a, b in zip(pattern_A, pattern_B):
                if a > b:
                    cnt += 1
            if n - cnt < cnt:
                win += 1
    print(win / total)


if __name__ == '__main__':
    resolve()