n, k = map(int, input().split())
lst = list(map(int, input().split()))
temp = sum(lst[:k])
m = sum(lst[:k])
for i in range(k, n):
  temp = temp - lst[i - k] + lst[i]
  m = max(m, temp)
print((m + k) / 2) n, k = map(int, input().split()) n map(int, input().split()) map int input().split() ().split () input split k lst = list(map(int, input().split())) lst list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split temp = sum(lst[:k]) temp sum(lst[:k]) sum lst[:k] lst :k k m = sum(lst[:k]) m sum(lst[:k]) sum lst[:k] lst :k k for i in range(k, n):
  temp = temp - lst[i - k] + lst[i]
  m = max(m, temp) i range(k, n) range k n temp = temp - lst[i - k] + lst[i] temp temp - lst[i - k] + lst[i] temp - lst[i - k] temp lst[i - k] lst i - k i k lst[i] lst i m = max(m, temp) m max(m, temp) max m temp print((m + k) / 2) print (m + k) / 2 m + k m k 2 temp = temp - lst[i - k] + lst[i] temp - lst[i - k] + lst[i] temp n, k = map(int, input().split()) map(int, input().split()) n m = sum(lst[:k]) sum(lst[:k]) m k = map(int, input().split()) map(int, input().split()) k m = max(m, temp) max(m, temp) m lst = list(map(int, input().split())) list(map(int, input().split())) lst temp = sum(lst[:k]) sum(lst[:k]) temp
n, k = map(int, input().split())
lst = list(map(int, input().split()))
temp = sum(lst[:k])
m = sum(lst[:k])
for i in range(k, n):
  temp = temp - lst[i - k] + lst[i]
  m = max(m, temp)
print((m + k) / 2)