import itertools
import math

def main():
    N = int(input())
    A = list(map(int, input().split()))
    B = list(map(int, input().split()))

    win = 0

    for p in itertools.permutations(B):
        wp = 0
        for i in range(N):
            if A[i] > p[i]:
                wp += 1
        if wp > N / 2:
            win += 1

    ans = win / math.factorial(N)
    print(ans)

if __name__ == "__main__":
    main()