N, K = map(int, input().split())
P = list(map(int, input().split()))

score = sum(P[:K])
mmax = score
idx = 0
for i in range(1, N-K+1):
  score = score - P[i-1] + P[i+K-1]
  if score > mmax:
    mmax = score
    idx = i
  else:
    continue

print((K+mmax)/2) N, K = map(int, input().split()) N map(int, input().split()) map int input().split() ().split () input split K P = list(map(int, input().split())) P list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split score = sum(P[:K]) score sum(P[:K]) sum P[:K] P :K K mmax = score mmax score idx = 0 idx 0 for i in range(1, N-K+1):
  score = score - P[i-1] + P[i+K-1]
  if score > mmax:
    mmax = score
    idx = i
  else:
    continue i range(1, N-K+1) range 1 N-K+1 N-K N K 1 score = score - P[i-1] + P[i+K-1] score score - P[i-1] + P[i+K-1] score - P[i-1] score P[i-1] P i-1 i 1 P[i+K-1] P i+K-1 i+K i K 1 if score > mmax:
    mmax = score
    idx = i
  else:
    continue score > mmax score mmax mmax = score mmax score idx = i idx i continue print((K+mmax)/2) print (K+mmax)/2 K+mmax K mmax 2 score = sum(P[:K]) sum(P[:K]) score score = score - P[i-1] + P[i+K-1] score - P[i-1] + P[i+K-1] score mmax = score score mmax N, K = map(int, input().split()) map(int, input().split()) N mmax = score score mmax idx = 0 0 idx idx = i i idx K = map(int, input().split()) map(int, input().split()) K P = list(map(int, input().split())) list(map(int, input().split())) P
N, K = map(int, input().split())
P = list(map(int, input().split()))

score = sum(P[:K])
mmax = score
idx = 0
for i in range(1, N-K+1):
  score = score - P[i-1] + P[i+K-1]
  if score > mmax:
    mmax = score
    idx = i
  else:
    continue

print((K+mmax)/2)