from itertools import permutations
n=int(input())
a=list(permutations(list(map(int,input().split()))))
b=list(permutations(list(map(int,input().split()))))
ca=0
ct=0
for i in range(len(a)):
  for j in range(len(b)):
    cnta=0
    cntb=0
    for l,m in zip(a[i],b[j]):
      if l>m:cnta+=1
      else:cntb+=1
    if cnta>cntb:ca+=1
    ct+=1
print(ca/ct)