a,b = input().split(" ")
a = int(a)
b = int(b)
c = []
c = map(int,input().split(" "))
d = list(c)
f = []
result = 0
answer = []
dap = 0
##print(d)
for i in range(0,len(d)-b+1):
    for j in range(i,b+i):
        result = result + d[j]
    answer.append(result)
    result = 0
print(answer)
for k in range(0,len(answer)):
    if answer[k] > dap:
        dap = answer[k]
print(dap)