n,k = map(int,input().split())
a = list(map(int,input().split()))
ans = 0
from collections import defaultdict
import heapq
d = defaultdict(int)
sum_ = 0
q = []
for i,e in enumerate(sorted(set(a))):
    d[e] = i + 1
for i in range(n-1,0,-1):
    if i & 1:
        ans = max(ans ,a[i] + sum_)
        heapq.heappush(q,a[i])
    else:
        heapq.heappush(q,a[i])
    sum_ += a[i]
    if len(q) > k-1:
        sum_ -= heapq.heappop(q)
print(ans)