n = int(input())
v = list(map(int,input().split()))
v.sort()

while n != 1:
  sign = n%2
  temp = []
  
  if sign == 0:
    for i in range(n//2):
      temp.append((v[2*i]+v[2*i+1])/2)
      
  elif sign == 1:
    for i in range((n-1)//2):
      temp.append((v[2*i]+v[2*i+1])/2)
      
    temp.append(v[n-1])
    
  n = len(temp)
  v = temp
  
print(v[0])