defmodule Int do
	def fac(n, m) do
		ans = []
		cond do
			m*m > n -> ans ++ [n]
			rem(n, m) == 0 -> ans ++ [m] ++ (div(n, m) |> fac(m))
			true -> ans ++ fac(n, m+1)
		end
	end
end

defmodule Comb do
	def permutations(n, n_remain, used) do
		ans =
		for x <- 1..n do
			if Enum.at(used, x-1) == false do
				ps = permutations(n, n_remain-1, List.replace_at(used, x-1, true))
				case n_remain <= 1 do
					true -> [x]
					_ -> Enum.map(ps, fn p ->  List.insert_at(p, -1, x) end)
				end
			end
		end
		|> Enum.filter(fn p -> p != nil end)
		|> List.flatten
		case n_remain > 1 do
			true -> Enum.chunk(ans, n_remain)
			_ -> [ans]
		end
	end
end

defmodule Prob do
	def judge(a, b, pa, pb) do
		result =
		for x <- 1..length(a) do
			Enum.at(a, Enum.at(pa, x-1)-1) > Enum.at(b, Enum.at(pb, x-1)-1)
		end
		length(Enum.filter(result, fn r -> r == true end))*2 > length(a)
	end
end

defmodule Main do
	def main do
		n = IO.gets("") |> String.trim() |> String.to_integer
		used =  for _ <- 1..n, do: false
		p = Comb.permutations(n, n, used)
		q = p
		a = IO.gets("") |> String.trim()  |> String.split(" ") |> Enum.map(fn s -> String.to_integer(s) end)
		b = IO.gets("") |> String.trim()  |> String.split(" ") |> Enum.map(fn s -> String.to_integer(s) end)
		result = for pa <- p, pb <- q, do: Prob.judge(a, b, pa, pb)
		ans = length(Enum.filter(result, fn r -> r == true end))/length(result)
		IO.inspect(ans)
	end
end