import sys

stdin = sys.stdin

ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
ns = lambda: stdin.readline().rstrip()  # ignore trailing spaces

n = ni()
v = na()
v.sort()

s = 0
for i in range(n):
    s = s * 0.5 + v[i]
    if i == 0:
        s += v[i]
print(f"{s*0.5:.14f}")