N = int(input())

v = list(map(int,input().split()))
         
if N == 2:
  print(sum([int(i) for i in v])/2)
  exit()
  
else:
  r = []
  for a in range(N):
    s = sum([elem for idx,elem in enumerate(v) if idx != a])/(N-1)
    r.append((v[a]+s)/2)

print(max(r))