# 今回は N は不要
N = gets.to_i
As = gets.split.map(&:to_i).sort

# 偶数か奇数かを判定する
if N.odd?
  t = N/2
  puts As[t]

else
  t1 = N/2
  t2 = t1-1
  puts (As[t1] + As[t2])/2.0
end