N = int(input())
x = list(map(int,input().split()))
x.sort()
p = []

while True:
  for j in range(0,N,2):
    if len(x)%2 == 0:
      p.append((x[j] + x[j+1])/2) 
    else:
      if j != N-1:
        p.append((x[j] + x[j + 1]) / 2)
      else:
        p.append(x[-1])
    
      
  else:
    x = p
    if len(p) == 1:
      break
    p = []
    N = len(x)
print(p[0])
  