N = gets.to_i
A = gets.split.map(&:to_i)
B = gets.split.map(&:to_i)

win = 0
count = 0

A.permutation do |a|
  B.permutation do |b|
    w = N.times.count{|i| a[i] > b[i] }
    win += 1 if w > N - w
    count += 1
  end
end

puts win.to_f / count