N = gets.to_i
cards_a = gets.split.map(&:to_i)
cards_b = gets.split.map(&:to_i)

cnt = 0
total = 0

cards_a.permutation do |perm_a|
  cards_b.permutation do |perm_b|
    total += 1
    vic_a = 0
    vic_b = 0

    N.times do |i|
      a = perm_a[i]
      b = perm_b[i]

      if a > b
        vic_a += 1
      elsif b > a
        vic_b += 1
      end
    end

    cnt += 1 if vic_a > vic_b
  end
end

p cnt.to_f / total