N = int(input())
hoge = input().split()
v = []
for i in range(N):
  v.append(int(hoge[i]))

_v = sorted(v, reverse=True)

gu = _v.pop(N-1)
if N == 2:
  print((_v[0]+_v[1])/2)
else:
  for i in range(N-2,-1,-1):
    gu = (gu + _v.pop(i))/2
  print(gu)