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

rwa = [0]*(len(p)+1)

for i in range(len(rwa)-1):
    rwa[i+1] = rwa[i]+p[i]

wa = [0]*(N-K+1)
for i in range(len(wa)):
    wa[i] = rwa[K+i]-rwa[i]

t = wa.index(max(wa))

re = 0
for i in range(K):
    if p[t+i]%2 == 0:
        re += p[t+i]/2 +0.5
    else:
        re += p[t+i]//2 +1


print(re) 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 rwa = [0]*(len(p)+1) rwa [0]*(len(p)+1) [0] 0 len(p)+1 len(p) len p 1 for i in range(len(rwa)-1):
    rwa[i+1] = rwa[i]+p[i] i range(len(rwa)-1) range len(rwa)-1 len(rwa) len rwa 1 rwa[i+1] = rwa[i]+p[i] rwa[i+1] rwa i+1 i 1 rwa[i]+p[i] rwa[i] rwa i p[i] p i wa = [0]*(N-K+1) wa [0]*(N-K+1) [0] 0 N-K+1 N-K N K 1 for i in range(len(wa)):
    wa[i] = rwa[K+i]-rwa[i] i range(len(wa)) range len(wa) len wa wa[i] = rwa[K+i]-rwa[i] wa[i] wa i rwa[K+i]-rwa[i] rwa[K+i] rwa K+i K i rwa[i] rwa i t = wa.index(max(wa)) t wa.index(max(wa)) wa.index wa index max(wa) max wa re = 0 re 0 for i in range(K):
    if p[t+i]%2 == 0:
        re += p[t+i]/2 +0.5
    else:
        re += p[t+i]//2 +1 i range(K) range K if p[t+i]%2 == 0:
        re += p[t+i]/2 +0.5
    else:
        re += p[t+i]//2 +1 p[t+i]%2 == 0 p[t+i]%2 p[t+i] p t+i t i 2 0 re += p[t+i]/2 +0.5 re p[t+i]/2 +0.5 p[t+i]/2 p[t+i] p t+i t i 2 0.5 re += p[t+i]//2 +1 re p[t+i]//2 +1 p[t+i]//2 p[t+i] p t+i t i 2 1 print(re) print re p = list(map(int,input().split())) list(map(int,input().split())) p N,K = map(int,input().split()) map(int,input().split()) N re += p[t+i]//2 +1 p[t+i]//2 +1 re wa = [0]*(N-K+1) [0]*(N-K+1) wa re = 0 0 re re += p[t+i]/2 +0.5 p[t+i]/2 +0.5 re rwa = [0]*(len(p)+1) [0]*(len(p)+1) rwa t = wa.index(max(wa)) wa.index(max(wa)) t K = map(int,input().split()) map(int,input().split()) K
N,K = map(int,input().split())
p = list(map(int,input().split()))

rwa = [0]*(len(p)+1)

for i in range(len(rwa)-1):
    rwa[i+1] = rwa[i]+p[i]

wa = [0]*(N-K+1)
for i in range(len(wa)):
    wa[i] = rwa[K+i]-rwa[i]

t = wa.index(max(wa))

re = 0
for i in range(K):
    if p[t+i]%2 == 0:
        re += p[t+i]/2 +0.5
    else:
        re += p[t+i]//2 +1


print(re)
