N, K = map(int, input().split())
p = list(map(int, input().split()))
ans = [sum(p[:K])]
for i in range(N-K):
  ans.append(ans[-1]-p[i]+p[i+K])
print(max(ans)/2+K/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 ans = [sum(p[:K])] ans [sum(p[:K])] sum(p[:K]) sum p[:K] p :K K for i in range(N-K):
  ans.append(ans[-1]-p[i]+p[i+K]) i range(N-K) range N-K N K ans.append(ans[-1]-p[i]+p[i+K]) ans.append ans append ans[-1]-p[i]+p[i+K] ans[-1]-p[i] ans[-1] ans -1 p[i] p i p[i+K] p i+K i K print(max(ans)/2+K/2) print max(ans)/2+K/2 max(ans)/2 max(ans) max ans 2 K/2 K 2 p = list(map(int, input().split())) list(map(int, input().split())) p K = map(int, input().split()) map(int, input().split()) K N, K = map(int, input().split()) map(int, input().split()) N ans = [sum(p[:K])] [sum(p[:K])] ans
N, K = map(int, input().split())
p = list(map(int, input().split()))
ans = [sum(p[:K])]
for i in range(N-K):
  ans.append(ans[-1]-p[i]+p[i+K])
print(max(ans)/2+K/2)