n = int(input())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
seen = [0 for i in range(2*n)]
p = []
num = []
win_count = 0
match_count = 0
def dfs(x):
    global win_count
    global match_count
    if sum(seen) == 2*n:
        count = 0
        for i in range(n):
            if a[p[i]] > b[p[i+n]-n]:
                count += 1
        if count / n > 0.50:
            win_count += 1
        match_count += 1
        return

    for i in range(2*n):
        length = len(p)
        if length < n and i < n:
            if seen[i] == 0:
                seen[i] = 1
                p.append(i)
                dfs(i)
                seen[i] = 0
                p.pop()
        if length >= n and i >= n:
            if seen[i] == 0:
                seen[i] = 1
                p.append(i)
                dfs(i)
                seen[i] = 0
                p.pop()

for i in range(n):
    seen[i] = 1
    p.append(i)
    dfs(i)
    seen[i] = 0
    p.pop()
print(win_count / match_count)