import heapq
N, K = map(int, input().split())
A = list(map(int, input().split()))
K2 = (K - 1) // 2 * 2 + 2 - (K & 1)
X = A[N - K2:N]
if K == 1:
    print(max(A[1:N:2]))
    exit()
heapq.heapify(X)
while len(X) > K - 1:
    heapq.heappop(X)
tmp = sum(X)
ans = A[1] + tmp
for i in reversed(range(1, N - K2, 2)):
    ans = max(ans, A[i] + tmp)
    if i == 1:
        break
    for j in range(2):
        tmp2 = heapq.heappop(X)
        a = A[i - j]
        if tmp2 > a:
            heapq.heappush(X, tmp2)
        else:
            tmp += a - tmp2
            heapq.heappush(X, a)
print(ans)