from collections import deque
import itertools

N = int(input())
V = list(map(int, input().split()))
l = list(itertools.permutations(V))
r = list()
for lo in l:
    d = deque(lo)
    while(len(d) != 1):
        d.append((d.pop() + d.pop()) / 2)
    r.append(d)
print(max(r).pop())
