997 B | 997 chars
"""
[15577: Prosjek](https://www.acmicpc.net/problem/15577)
Tier: Silver 4
Category: data_structures, greedy, math, priority_queue, sorting
"""
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
SYS_INPUT = True
RECURSION_LIMIT = 10 ** 7
SET_RECURSION = False
BLANK = " "
if SET_RECURSION:
sys.setrecursionlimit(RECURSION_LIMIT)
inp = lambda : sys.stdin.readline().rstrip() if SYS_INPUT else input()
mii = lambda : [*map(int,inp().split())]
mfi = lambda : [*map(float,inp().split())]
ii = lambda : int(inp())
fi = lambda : float(inp())
isplit = lambda : inp().split()
p = print
def gcd(a, b): return gcd(b, a % b) if b > 0 else a
def lcm(a, b): return a * b // gcd(a, b)
def solve():
n = ii()
l = [ii() for _ in range(n)]
while len(l) > 1:
l.sort()
k = (l[0] + l[1]) / 2
l = [k] + l[2:]
ans = l[0]
print(f"{ans:.6f}")
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()