N = int(input())
e = list(map(int,input().split()))
for i in range(N):
    x = int(input())
    e.append(x)
e.sort()
for i in range(N - 1):
    a = e.pop(0)
    b = e.pop(0)
    e.insert(0, (a+b)/2)
ans = e[0]
print(ans)