n, k = map(int, input().split())
p = list(map(lambda x: int(x) + 1, input().split()))

s = 0
e = k
t = sum(p[0:k])

ans = 0
while True:
    ans = max(ans, t)
    if e == n:
        break
    t -= p[s]
    t += p[e]
    s += 1
    e += 1

print(ans / 2) n, k = map(int, input().split()) n map(int, input().split()) map int input().split() ().split () input split k p = list(map(lambda x: int(x) + 1, input().split())) p list(map(lambda x: int(x) + 1, input().split())) list map(lambda x: int(x) + 1, input().split()) map lambda x: int(x) + 1 int(x) + 1 int(x) int x 1 x input().split() ().split () input split s = 0 s 0 e = k e k t = sum(p[0:k]) t sum(p[0:k]) sum p[0:k] p 0:k 0 k ans = 0 ans 0 while True:
    ans = max(ans, t)
    if e == n:
        break
    t -= p[s]
    t += p[e]
    s += 1
    e += 1 True ans = max(ans, t) ans max(ans, t) max ans t if e == n:
        break
     e == n e n break t -= p[s] t p[s] p s t += p[e] t p[e] p e s += 1 s 1 e += 1 e 1 print(ans / 2) print ans / 2 ans 2 t += p[e] p[e] t e = k k e e += 1 1 e p = list(map(lambda x: int(x) + 1, input().split())) list(map(lambda x: int(x) + 1, input().split())) p s = 0 0 s n, k = map(int, input().split()) map(int, input().split()) n ans = 0 0 ans k = map(int, input().split()) map(int, input().split()) k t -= p[s] p[s] t ans = max(ans, t) max(ans, t) ans s += 1 1 s t = sum(p[0:k]) sum(p[0:k]) t
n, k = map(int, input().split())
p = list(map(lambda x: int(x) + 1, input().split()))

s = 0
e = k
t = sum(p[0:k])

ans = 0
while True:
    ans = max(ans, t)
    if e == n:
        break
    t -= p[s]
    t += p[e]
    s += 1
    e += 1

print(ans / 2)
