#yukicoderNO.113
n=int(input())
a=list(map(int,input().split()))
b=list(map(int,input().split()))

def makepop(now,card,ans):
    if len(card)==0:
        ans.append(now)
        return ans
    for i in range(len(card)):
        nextcard=card.copy()
        x=nextcard.pop(i)
        nex=now+[x]
        ans=makepop(nex,nextcard,ans)
    return ans
apop=makepop([],a,[])
bpop=makepop([],b,[])
win,match=0,0
def battle(x,y):
    point=0
    for i in range(len(x)):
        if x[i]>y[i]:point+=1
    if point>len(x)/2:return 1
    else:return 0
for x in apop:
    for y in bpop:
        win+=battle(x,y)
        match+=1
print(win/match)