import heapq

N, M = list(map(int,input().split()))
T = list(map(int,input().split()))

HQ = []
heapq.heapify(HQ)

servers = 1
heapq.heappush(HQ, T[0])
for i in range(1, N):
    if servers < M:
        heapq.heappush(HQ, T[i])
        servers += 1
    else:
        p = heapq.heappop(HQ)
        heapq.heappush(HQ, p + T[i])

print(max(HQ))