import itertools
N = int(input())
lsA = list(map(int,input().split()))
lsB = list(map(int,input().split()))
lspa = itertools.permutations(lsA,N)
lspb = itertools.permutations(lsB,N)

cntall = 0
cntwin = 0
for A in lspa:
    for B in lspb:
        point = 0
        for i in range(N):
            if A[i] > B[i]:
                point += 1
        if point > N//2:
            cntwin += 1
        cntall += 1
print(cntwin/cntall)