from collections import deque
n = int(input())
value = list(map(int, input().split(" ")))
value.sort()
value = deque(value)
que = deque()
ans = 0
a = value.popleft()
b = value.popleft()
c = (a+b)/2
que.append(c)
while value:
  a = value.popleft()
  if value:
    b = value.popleft()
    c = que.popleft()
    if b <= c:
      que.append(c)
      c = (a+b)/2
      que.append(c)
    else:
      value.appendleft(b)
      c = (a+c)/2
      que.append(c)
  else:
    c = que.popleft()
    c = (a+c)/2
    que.append(c)
ans = que[0]
print(ans)
  