n,k=map(int,input().split())
a=list(map(int,input().split()))
b=[0]*n
m=0

for i in range(n):
    b[i]=(a[i]+1)/2

c=sum(b[:k])
m=c
for i in range(n-k):
    c-=b[i]
    c+=b[k+i]
    m=max(m,c)
print(m) n,k=map(int,input().split()) n map(int,input().split()) map int input().split() ().split () input split k a=list(map(int,input().split())) a list(map(int,input().split())) list map(int,input().split()) map int input().split() ().split () input split b=[0]*n b [0]*n [0] 0 n m=0 m 0 for i in range(n):
    b[i]=(a[i]+1)/2 i range(n) range n b[i]=(a[i]+1)/2 b[i] b i (a[i]+1)/2 a[i]+1 a[i] a i 1 2 c=sum(b[:k]) c sum(b[:k]) sum b[:k] b :k k m=c m c for i in range(n-k):
    c-=b[i]
    c+=b[k+i]
    m=max(m,c) i range(n-k) range n-k n k c-=b[i] c b[i] b i c+=b[k+i] c b[k+i] b k+i k i m=max(m,c) m max(m,c) max m c print(m) print m m=0 0 m m=max(m,c) max(m,c) m k=map(int,input().split()) map(int,input().split()) k a=list(map(int,input().split())) list(map(int,input().split())) a c=sum(b[:k]) sum(b[:k]) c c-=b[i] b[i] c m=c c m c+=b[k+i] b[k+i] c n,k=map(int,input().split()) map(int,input().split()) n b=[0]*n [0]*n b
n,k=map(int,input().split())
a=list(map(int,input().split()))
b=[0]*n
m=0

for i in range(n):
    b[i]=(a[i]+1)/2

c=sum(b[:k])
m=c
for i in range(n-k):
    c-=b[i]
    c+=b[k+i]
    m=max(m,c)
print(m)