def main():
  import sys
  from collections import deque
  n=int(input())
  v=list(map(int,sys.stdin.read().split()))
  w=deque(sorted(v))
  ans=(w.popleft()+w.popleft())/2
  for i in range(n-2):
    ans+=w.popleft()/2
  print(ans)
if __name__=="__main__":
  main()