n, k = map(int, input().split())
P = list(map(int, input().split()))

P_ac = [sum(P[:k])]
for i in range(n-k):
    P_ac.append(P_ac[-1]-P[i]+P[i+k])

print((max(P_ac)+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 P_ac = [sum(P[:k])] P_ac [sum(P[:k])] sum(P[:k]) sum P[:k] P :k k for i in range(n-k):
    P_ac.append(P_ac[-1]-P[i]+P[i+k]) i range(n-k) range n-k n k P_ac.append(P_ac[-1]-P[i]+P[i+k]) P_ac.append P_ac append P_ac[-1]-P[i]+P[i+k] P_ac[-1]-P[i] P_ac[-1] P_ac -1 P[i] P i P[i+k] P i+k i k print((max(P_ac)+k)/2) print (max(P_ac)+k)/2 max(P_ac)+k max(P_ac) max P_ac k 2 P = list(map(int, input().split())) list(map(int, input().split())) P n, k = map(int, input().split()) map(int, input().split()) n P_ac = [sum(P[:k])] [sum(P[:k])] P_ac k = map(int, input().split()) map(int, input().split()) k
n, k = map(int, input().split())
P = list(map(int, input().split()))

P_ac = [sum(P[:k])]
for i in range(n-k):
    P_ac.append(P_ac[-1]-P[i]+P[i+k])

print((max(P_ac)+k)/2)