n, k = map(int, input().split())
p = list(map(int, input().split()))
s = sum(p[:k])
ret = s
for i in range(k, n):
    s += p[i] - p[i - k]
    ret = max(ret, s)
print((ret + k) / 2.0) 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 s = sum(p[:k]) s sum(p[:k]) sum p[:k] p :k k ret = s ret s for i in range(k, n):
    s += p[i] - p[i - k]
    ret = max(ret, s) i range(k, n) range k n s += p[i] - p[i - k] s p[i] - p[i - k] p[i] p i p[i - k] p i - k i k ret = max(ret, s) ret max(ret, s) max ret s print((ret + k) / 2.0) print (ret + k) / 2.0 ret + k ret k 2.0 k = map(int, input().split()) map(int, input().split()) k s = sum(p[:k]) sum(p[:k]) s ret = s s ret p = list(map(int, input().split())) list(map(int, input().split())) p s += p[i] - p[i - k] p[i] - p[i - k] s n, k = map(int, input().split()) map(int, input().split()) n ret = max(ret, s) max(ret, s) ret
n, k = map(int, input().split())
p = list(map(int, input().split()))
s = sum(p[:k])
ret = s
for i in range(k, n):
    s += p[i] - p[i - k]
    ret = max(ret, s)
print((ret + k) / 2.0)
