20250813

# n=int(input())
# arr=list(map(int, input().split()))
# arr.sort()
# arr.reverse()
# for i in range (n):
#     print(arr[i], end=' ')

n,k=map(int, input().split())
arr=list(map(int, input().split()))
sum=-200
pl=0


for i in range(n-(k-1)):
    if n==k:
        print(arr[i]+arr[i+1])
        exit()
    pl=0
    for j in range(k):

        pl=pl+arr[i+j]
        if pl>sum:
            sum=pl
print(sum)