import re

n = int(input())
v = sorted(list(map(int, input().split())))

ans = (v[0]+v[1])/2

if n == 2:
    ans = str(ans)

elif n > 2 and n % 2 == 0:
    for i in range(n/2):
        ans = str((ans + v[i+2])/2)

else:
    for i in range(n-2):
        ans = str((ans + v[i+2])/2)

if re.search('.0', ans):
   ans = ans.replace('.0', '')
   print(ans)

else:
    print(ans)