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

arr = [(1 + m) / 2 for m in p]
ans = 0
sum = 0
for i in range(n):
	sum += arr[i]
	if i >= k: sum -= arr[i - k] 
	ans = max(ans, sum)
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 + m) / 2 for m in p for m in p m p for m in p (1 + m) / 2 1 + m 1 m 2 arr = [(1 + m) / 2 for m in p] arr [(1 + m) / 2 for m in p] ans = 0 ans 0 sum = 0 sum 0 for i in range(n):
	sum += arr[i]
	if i >= k: sum -= arr[i - k] 
	ans = max(ans, sum) i range(n) range n sum += arr[i] sum arr[i] arr i if i >= k: sum -= arr[i - k] 
	 i >= k i k ans = max(ans, sum) ans max(ans, sum) max ans sum print(ans) print ans sum = 0 0 sum sum += arr[i] arr[i] sum ans = max(ans, sum) max(ans, sum) ans k = map(int, input().split()) map(int, input().split()) k ans = 0 0 ans n, k = map(int, input().split()) map(int, input().split()) n p = list(map(int, input().split())) list(map(int, input().split())) p arr = [(1 + m) / 2 for m in p] [(1 + m) / 2 for m in p] arr
n, k = map(int, input().split())
p = list(map(int, input().split()))

arr = [(1 + m) / 2 for m in p]
ans = 0
sum = 0
for i in range(n):
	sum += arr[i]
	if i >= k: sum -= arr[i - k] 
	ans = max(ans, sum)
print(ans)
