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