def narabe(N, li):
    if N == 1:
        return [[li[0]]]
    result_lists = []
    bef_narabe = narabe(N - 1, li)
    for i in range(len(bef_narabe)):
        for j in range(N):
            bef_li = [] + bef_narabe[i]
            bef_li.insert(j, li[N - 1])
            narabe_li = bef_li
            result_lists.append(narabe_li)
    return result_lists

def shobu(N, li_a, li_b):
    narabe_a = narabe(N, li_a)
    narabe_b = narabe(N, li_b)
    cnt_a = 0
    n1 = len(narabe_a)
    for k in range(n1):
        n2 = len(narabe_a[k])
        for l in range(len(narabe_b)):
            cnt_a_k = 0
            for m in range(n2):
                if narabe_a[k][m] > narabe_b[l][m]:
                    cnt_a_k += 1
            if cnt_a_k > n2 / 2:
                cnt_a += 1
    result = cnt_a / (n1 ** 2)
    return result

def main():
    N = int(input())
    li_a = list(map(int, input().split()))
    li_b = list(map(int, input().split()))
    print(shobu(N, li_a, li_b))

if __name__ == '__main__':
    main()