# require 'pry'

N = gets.chomp.to_i
V = gets.chomp.split(' ').map(&:to_i)


denominator = 2**(N-1)

V.sort!

@sum = 0
V.each_with_index do |v, i|
  if i < 2
    @sum += v
  else
    @sum += v*(2**(i-1))
  end
end

puts ans = @sum.to_f / denominator


# binding.pry
