# import sys
# readline = sys.stdin.buffer.readline

from collections import deque
from copy import copy,deepcopy
from itertools import permutations,combinations

def myinput():
    return map(int,input().split())

def mycol(data,col):
    return [ row[col] for row in data ]

n = int(input())
a = list(myinput())
b = list(myinput())

pa = list(permutations(a))
pb = list(permutations(b))
# print(pa)
# print(pb)

count_win_a = 0
count_win_b = 0
count_match = 0
for pattern_a in pa:
    for pattern_b in pb:
        count_match += 1
        count_a = 0
        count_b = 0
        for i in range(n):
            card_a = pattern_a[i]
            card_b = pattern_b[i]
            if card_a > card_b:
                count_a += 1
            else:
                count_b += 1
        if count_a > count_b:
            count_win_a += 1
        elif count_a==count_b:
            pass
        else:
            count_win_b += 1
# print(count_win_a,count_match)
ans = count_win_a/count_match
print(ans)