import sys
import itertools
stdin=sys.stdin

ip=lambda: int(sp())
fp=lambda: float(sp())
lp=lambda:list(map(int,stdin.readline().split()))
sp=lambda:stdin.readline().rstrip()
Yp=lambda:print('Yes')
Np=lambda:print('No')

N = ip()
A = lp()
B = lp()

P = list(itertools.permutations(A,N))
Q = list(itertools.permutations(B,N))

All = len(P) * len(Q)
win = 0

for a in P:
    for b in Q:
        res = 0
        for turn in range(N):
            if a[turn] > b[turn]:
                res += 1
        if res > N - res:
            win += 1

print(win / All)