n = int(input())
v = list(map(int, input().split()))

while len(v) != 2:
    sorted(v)
    ave =  (v[0]+v[1])/2
    v.remove(v[0])
    v.remove(v[1])
    v.append(ave)

if len(v) == 2:
    print((v[0]+v[1])/2)