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)
  
ans = a[0]

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

print(ans)