import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
sys.setrecursionlimit(10 ** 7)

from itertools import accumulate

n, k, *a = map(int, read().split())
cumsum = [0] + list(accumulate(a))
ans = -float('inf')
for kk in range(1, k + 1):
    for bf, af in zip(cumsum, cumsum[kk:]):
        ans = max(ans, af - bf)
print(ans)