num = gets.to_i
input = gets.to_s.split(" ").map(&:to_i)
answer = 0
for i in 0..num-2 do
  min1 = input.min
  min_index1 = input.index(min1)
  input.delete_at(min_index1)

  min2 = input.min
  min_index2 = input.index(min2)

  input.delete_at(min_index2)
  answer = (min1 + min2) / 2.to_f

  input.push(answer)

end

puts input