from itertools import permutations
def calc(N,A,B):
    win = 0
    al = list(permutations(range(N)))
    total = len(al)
    for v in al:
        a = 0
        b = 0
        for i in v:
            if A[i] > B[i]:
                a += 1
            elif A[i] < B[i]:
                b += 1
        if a > b:
            win += 1
    return win/total
def main():
    N = int(input())
    A = list(map(int,input().split(" ")))
    B = list(map(int,input().split(" ")))
    print(calc(N,A,B))

if __name__ == '__main__':
    main()