import numpy as np
a = int(input())
b = np.array([int(i) for i in input().split()])
b = np.sort(b)
while len(b) != 1:
  c = np.delete(b,0)
  c = np.delete(c,0)
  c = np.append(c,(b[0] + b[1])/2)
  b = np.sort(c)
print(b)