n = int(input())

#1~N
V = list(map(int,input().split()))

V.sort()

a = []

tmp = 0

for v in V:
  if tmp == v:
    continue
  tmp = v
  a.append(v)
  
if len(a) == 1:
  print(a[0])
  exit()
  
#b = []
#cnt = 0
#for i in range(len(a)-1):
#  b.append( (a[i+1] - a[i],cnt) )
#  cnt += 1
  
#sorted(b)
  
#print(b)

#tmp = a[b[0][1]]
l = len(a)

for i in range(l-1):
  b = []
  cnt = 0
  if len(b) == 1:
    break
  for j in range(l-i-1):
    b.append( (a[j+1] - a[j],cnt) )
    cnt += 1
  sorted(b)
#  l2 = len(a)
#  print("a = {}".format(a))
#  print("b[0][1] = {}".format(b[0][1]))
  ans = (a[b[0][1]] + a[b[0][1]+1])/2
  a.pop(b[0][1])
  a.pop(b[0][1])
  a.insert(0,ans)

#ans = a[0]

#for i in range(len(a)-1):
#  ans = (ans + a[i+1])/2
  

print(a[0])