N = input()
a = input()
Ni = int(N)-1
l = a.split()
temp = 0

for i in reversed(range(int(N))):
  for j in range(i):
    if l[j] > l[j+1]:
      l[j],l[j+1] = l[j+1],l[j]

for i in range(int(Ni)):
  temp = (int(l[i])+int(l[i+1]))/2
  del l[:1]
  l.insert(1, temp)
  
print(temp)