n = int(input())
value_list = sorted([ int(v) for v in input().split() ])
for i in range(n-1):
    a = value_list[0]
    b = value_list[1]
    for j in range(2):
        del value_list[0]
    c = (a+b)/2
    value_list.append(c)
print(value_list[0])