import numpy as np
n = int(input())
v = [int(i) for i in input().split()]
v.sort()
for i in range(n): 
  if len(v) == 1:
    break
  v1 = v.pop(0)
  v2 = v.pop(0)
  v3 = (v1 + v2) / 2
  v.append(v3)
print(v[0])