N, K = map(int, input().split())
p = list(map(int, input().split()))

s = sum(p[:K])
ss = []
ss.append(s)

for i in range(N - K):
    s = s - p[i] + p[i+K]
    ss.append(s)

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

s = sum(p[:K])
ss = []
ss.append(s)

for i in range(N - K):
    s = s - p[i] + p[i+K]
    ss.append(s)

print(K + (max(ss) - K) / 2)