N = int(input())

v = list(map(int,input().split()))
         
if N == 2:
  print(sum([int(i) for i in v])/2)
  exit()
  
else:
  v.sort(reverse=True)
  a = v[0]
  v.pop(0)
  r = (a + (sum([int(i) for i in v])/(N-1))) / 2
  print(r)