import sys
input = sys.stdin.readline

N,K=map(int,input().split())
A=list(map(int,input().split()))

if K==N-1:
    print(sum(A[1:]))
    exit()

Ai = [(a,i) for i,a in enumerate(A)]

B = sorted(Ai[1:], reverse=True)
odd = []
even = []
ans = 0
for b,i in B[:K]:
    if i%2==0:
        odd.append((b,i))
    else:
        even.append((b,i))
    ans += b
odd.sort(key=lambda x:x[1])
even.sort(key=lambda x:x[1])
if K==1:
    ans = max([A[i] for i in range(1,N,2)])
elif len(even)==0:
    b,i = odd[1]
    Ao = [A[j] for j in range(1,i,2)]
    mx = max(Ao)
    ans += mx - b
elif len(odd)>0:
    if len(odd)==1:
        base = ans
        # oddを捨てる
        B = sorted([A[i] for i in range(1,N,2)], reverse=True)
        ans = sum(B[:K])
        # oddを生かす
        emin = min([e for e,i in even])
        B = [A[i] for i in range(1,odd[0][1],2)]
        ans = max(ans, base + max(B) - emin)

    elif odd[0][1]<even[0][1]:
        emin = min([e for e,i in even])
        base = ans
        # oddの先頭を捨てる　→　oddの２番目より前のevenの最大値を追加
        i = odd[1][1]
        ans = base + max([A[i] for i in range(1, i, 2)]) - odd[0][0]
        # oddの先頭を生かす　→　oddの1番目より前のevenの最大値を追加し、evenの最小値を引く
        ans = max(ans, base + max([A[i] for i in range(1, odd[0][1], 2)]) - emin)
print(ans)