# coding: utf-8

# submission # - User: herp_sy

# https://atcoder.jp/contests/



import math

import statistics



# fact(int)

def fact(n):

  if(n == 1):

    return 1

  else:

    return (n * fact(n - 1))



# gcd(int,int)

def gcd(a,b):

  if a == 0:

    return b

  elif b == 0:

    return a

  else:

    return gcd(b,a % b)



# lcm(int,int)

def lcm(a,b):

  return (a * b / gcd(a,b))



# qsort(array[])

def qsort(seq):

  if len(seq) < 1:

      return seq

  pivot = seq[0]

  left = []

  right = []

  for x in range(1, len(seq)):

    if seq[x] <= pivot:

        left.append(seq[x])

    else:

        right.append(seq[x])

  left = qsort(left)

  right = qsort(right)

  foo = [pivot]

  return (left + foo + right)



# = map(int, input().split())

n  = int(eval(input()))

#  = raw_input().split()

v  = list(int(i) for i in input().split())  

lastguzai = 0.00



for i in range(n):

  vs = sorted(v)

  if len(v) == 2:

    lastguzai = (v[0] + v[1]) / 2.00

    break

  # print(vs)

  v = vs

  lastguzai = (v[0] + v[1]) / 2.00

  del v[0]

  del v[0]

  

  v.append(lastguzai)

  # print(v)



print(('{:.6f}'.format(lastguzai)))

# coding: utf-8

# submission # - User: herp_sy

# https://atcoder.jp/contests/



import math

import statistics



def qsort(seq):

  if len(seq) < 1:

      return seq

  pivot = seq[0]

  left = []

  right = []

  for x in range(1, len(seq)):

    if seq[x] <= pivot:

        left.append(seq[x])

    else:

        right.append(seq[x])

  left = qsort(left)

  right = qsort(right)

  foo = [pivot]

  return (left + foo + right)



n  = int(eval(input()))

v  = list(int(i) for i in input().split())  

lastguzai = 0.00



for i in range(n):

  vs = sorted(v)

  if len(v) == 2:

    lastguzai = (v[0] + v[1]) / 2.00

    break

  v = vs

  lastguzai = (v[0] + v[1]) / 2.00

  del v[0:2]

  v.append(lastguzai)



print(('{:.6f}'.format(lastguzai)))

# coding: utf-8
# submission # - User: herp_sy
# https://atcoder.jp/contests/
import math
import statistics

# fact(int)
def fact(n):
    if n == 1:
        return 1
    else:
        return n * fact(n - 1)


# gcd(int,int)
def gcd(a, b):
    if a == 0:
        return b
    elif b == 0:
        return a
    else:
        return gcd(b, a % b)


# lcm(int,int)
def lcm(a, b):
    return a * b / gcd(a, b)


# qsort(array[])
def qsort(seq):
    if len(seq) < 1:
        return seq
    pivot = seq[0]
    left = []
    right = []
    for x in range(1, len(seq)):
        if seq[x] <= pivot:
            left.append(seq[x])
        else:
            right.append(seq[x])
    left = qsort(left)
    right = qsort(right)
    foo = [pivot]
    return left + foo + right


# = map(int, input().split())
n = int(eval(input()))
#  = raw_input().split()
v = list(int(i) for i in input().split())
lastguzai = 0.00
for i in range(n):
    vs = sorted(v)
    if len(v) == 2:
        lastguzai = (v[0] + v[1]) / 2.00
        break
    # print(vs)
    v = vs
    lastguzai = (v[0] + v[1]) / 2.00
    del v[0]
    del v[0]
    v.append(lastguzai)
    # print(v)
print(("{:.6f}".format(lastguzai)))

# coding: utf-8
# submission # - User: herp_sy
# https://atcoder.jp/contests/
import math
import statistics


def qsort(seq):
    if len(seq) < 1:
        return seq
    pivot = seq[0]
    left = []
    right = []
    for x in range(1, len(seq)):
        if seq[x] <= pivot:
            left.append(seq[x])
        else:
            right.append(seq[x])
    left = qsort(left)
    right = qsort(right)
    foo = [pivot]
    return left + foo + right


n = int(eval(input()))
v = list(int(i) for i in input().split())
lastguzai = 0.00
for i in range(n):
    vs = sorted(v)
    if len(v) == 2:
        lastguzai = (v[0] + v[1]) / 2.00
        break
    v = vs
    lastguzai = (v[0] + v[1]) / 2.00
    del v[0:2]
    v.append(lastguzai)
print(("{:.6f}".format(lastguzai)))

-# fact(int) -def fact(n): -    if n == 1: -        return 1 -    else: -        return n * fact(n - 1) - -# gcd(int,int) -def gcd(a, b): -    if a == 0: -        return b -    elif b == 0: -        return a -    else: -        return gcd(b, a % b) - - -# lcm(int,int) -def lcm(a, b): -    return a * b / gcd(a, b) - - -# qsort(array[]) -# = map(int, input().split()) -#  = raw_input().split() -    # print(vs) -    del v[0] -    del v[0] +    del v[0:2] -    # print(v)