n, m = map(int, input().split())
a = [int(v) for v in input().split()]

if n == 1:
    print(m * a[0])
else:
    s = 0
    step = []
    for v in a:
        s += v
        step.append(s)

    res = [0, 0]
    for k in range(1, m+1):
        res.append(max((step[i-1] if i == n and i != k + 1 else step[i-2])+res[k-i+1] for i in range(2, min(n, k+1)+1)))
    print(res[-1])