cnt = gets.chomp.to_i
numbers = gets.chomp.split
cnt.times do |i|
	numbers[i]=numbers[i].to_f
end
numbers.sort!
if numbers[0]==numbers[cnt-1]
	puts numbers[0]
else
	result=numbers[0]
	(cnt-1).times do |i|
		result=(result+numbers[i+1])/2
	end
	puts result
end