n = int(input())
v = list( map(int, input().split(" ")) )
v.sort(reverse=True)

answer = 0

if n == 2:
    answer = ((v[0]+v[1]) / 2)
else:
    for i in range(n):
        if i < 1:
            answer = ((v[i]+v[i+1]) / 2)
        else:
            answer = ((v[i]+answer) / 2)

print(answer)
