# inputs = readlines
inputs = "3\n500 300 200\n".split("\n")

n = inputs[0].to_i
vn = inputs[1].split(' ').map(&:to_i)

def solve(n, vn)
  vn.sort!
  sum = vn[0]
  (1..(n - 1)).each do |i|
    sum += vn[i]
    sum = sum / 2.0
  end
  sum
end

puts solve(n, vn)
