
N = gets.chomp.to_i

v = gets.chomp.split(" ").map(&:to_i)

v.sort!
work = 0
for i in 1..N-1 do
    if i == 1
        work = (v[i] + v[i-1]) / 2 
    else
        work = (work + v[i]) / 2
    end
end

puts work