import sys
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 63 - 1
mod = 998244353
hash_mod = 2147483647
dpos4 = ((1, 0), (0, 1), (-1, 0), (0, -1))
dpos8 = ((0, -1), (1, -1), (1, 0), (1, 1), (0, 1), (-1, 1), (-1, 0), (-1, -1))
from itertools import permutations
def main():
    N = ii()
    A = li()
    B = li()
    total = 0
    kati = 0
    for a_perm in permutations(range(N),N):
        for b_perm in permutations(range(N),N):
            a = 0
            b = 0
            for i in range(N):
                if A[a_perm[i]] > B[b_perm[i]]:
                    a += 1
                else:
                    b += 1
            if a > b:
                kati += 1

            total += 1

    print(kati/total)
                



if __name__ == '__main__':
    main()