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

a = [1+(i-1)/2 for i in p]
l = sum(a[:k])
ans = l
for i in range(1, n-k+1):
    l = l-a[i-1]+a[k+i-1]
    ans = max(ans, l)
print(ans) 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 1+(i-1)/2 for i in p for i in p i p for i in p 1+(i-1)/2 1 (i-1)/2 i-1 i 1 2 a = [1+(i-1)/2 for i in p] a [1+(i-1)/2 for i in p] l = sum(a[:k]) l sum(a[:k]) sum a[:k] a :k k ans = l ans l for i in range(1, n-k+1):
    l = l-a[i-1]+a[k+i-1]
    ans = max(ans, l) i range(1, n-k+1) range 1 n-k+1 n-k n k 1 l = l-a[i-1]+a[k+i-1] l l-a[i-1]+a[k+i-1] l-a[i-1] l a[i-1] a i-1 i 1 a[k+i-1] a k+i-1 k+i k i 1 ans = max(ans, l) ans max(ans, l) max ans l print(ans) print ans ans = max(ans, l) max(ans, l) ans l = sum(a[:k]) sum(a[:k]) l k = map(int, input().split()) map(int, input().split()) k a = [1+(i-1)/2 for i in p] [1+(i-1)/2 for i in p] a p = list(map(int, input().split())) list(map(int, input().split())) p n, k = map(int, input().split()) map(int, input().split()) n l = l-a[i-1]+a[k+i-1] l-a[i-1]+a[k+i-1] l ans = l l ans
n, k = map(int, input().split())
p = list(map(int, input().split()))

a = [1+(i-1)/2 for i in p]
l = sum(a[:k])
ans = l
for i in range(1, n-k+1):
    l = l-a[i-1]+a[k+i-1]
    ans = max(ans, l)
print(ans)