N, K = map(int, input().split())
P = [(int(x)+1)/2 for x in input().split()]

total=ans=sum(P[:K])
for n in range(K,N):
  total+=P[n]-P[n-K]
  ans=max(ans, total)

print(ans) N, K = map(int, input().split()) N map(int, input().split()) map int input().split() ().split () input split K (int(x)+1)/2 for x in input().split() for x in input().split() x input().split() ().split () input split for x in input().split() (int(x)+1)/2 int(x)+1 int(x) int x 1 2 P = [(int(x)+1)/2 for x in input().split()] P [(int(x)+1)/2 for x in input().split()] total=ans=sum(P[:K]) total sum(P[:K]) sum P[:K] P :K K =ans=sum(P[:K]) ans sum(P[:K]) for n in range(K,N):
  total+=P[n]-P[n-K]
  ans=max(ans, total) n range(K,N) range K N total+=P[n]-P[n-K] total P[n]-P[n-K] P[n] P n P[n-K] P n-K n K ans=max(ans, total) ans max(ans, total) max ans total print(ans) print ans K = map(int, input().split()) map(int, input().split()) K total=ans=sum(P[:K]) sum(P[:K]) total N, K = map(int, input().split()) map(int, input().split()) N total+=P[n]-P[n-K] P[n]-P[n-K] total P = [(int(x)+1)/2 for x in input().split()] [(int(x)+1)/2 for x in input().split()] P ans=max(ans, total) max(ans, total) ans ans=sum(P[:K]) sum(P[:K]) ans
N, K = map(int, input().split())
P = [(int(x)+1)/2 for x in input().split()]

total=ans=sum(P[:K])
for n in range(K,N):
  total+=P[n]-P[n-K]
  ans=max(ans, total)

print(ans)
