#https://atcoder.jp/contests/abc138/tasks/abc138_c

n=int(input())
v=list(map(int,input().split()))
v.sort()
while len(v)>1:
    a=v.pop(0)
    b=v.pop(0)
    v.append((a+b)/2)
    v.sort()
print(v[0])
