num = int(input())
lines = input().split(" ")
int_lines = [int(i) for i in lines]
int_lines.sort()
set_lines = set(int_lines)
count = 1

if num == 2:
  result = (int_lines[0] + int_lines[1]) / 2
  print(result)
elif len(set_lines) == 1:
  print(set_lines[0])
elif len(set_lines) == 2:
  result = (set_lines[0] + set_lines[1]) / 2
  print(result)
else:
  itr = iter([int(j) for j in list(set_lines)])
  for j in itr:
    if count == 1:
        x = j
        count += 1
    elif count == 2:
        y = j
        count += 1
    else:
        x = (x + y) / 2
        y = j
        count += 1
  x = (x + y) / 2
    
  print(x)