import sys
import numpy as np
import numba
from numba import jit

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

from heapq import heappop,heappush,heapify

@jit
def main(n, a):
  for _ in range(1, n):
    new = (a[1]+a[0])/2
    heappop(a)
    heappop(a)
    heappush(a, new)
  return new

n,*a = map(int,read().split())
heapify(a)
print(main(n,a))