from sys import stdin
N = int(stdin.readline().rstrip())
data = [int(x) for x in stdin.readline().rstrip().split()]
data = sorted(data)
if len(data) == 1:
    print(data[0])
else:
    while len(data) > 2:
        data.append(((data[0] + data[1]) / 2))
        data.remove(data[0])
        data.remove(data[1])
        data = sorted(data)
    print(sum(data)/2)