n = gets.to_i
a = gets.split.map(&:to_i)
b = gets.split.map(&:to_i)
win = 0
game = 0
a.permutation(n) do |i|
	b.permutation(n) do |j|
		t_win = 0
		t_lose = 0
		0.upto(n - 1) do |x|
			i[x] > j[x] ? t_win += 1 : t_lose += 1
		end
		win += 1 if t_win > t_lose
		game += 1
	end
end
p win.to_f / game