from itertools import permutations
from math import factorial

def main():
    n = int(input())
    A = list(map(int,input().split()))
    B = list(map(int,input().split()))
    ans = 0
    for prdA in permutations(range(n)):
        for prdB in permutations(range(n)):
            a,b = 0,0
            for i in range(n):
                if A[prdA[i]] > B[prdB[i]]:
                    a += 1
                elif A[prdA[i]] < B[prdB[i]]:
                    b += 1
            if a > b:
                ans += 1
    print(ans/factorial(n)/factorial(n))
if __name__ == '__main__':
    main()