import sys
input = sys.stdin.readline
import bisect

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

OK=0
NG=sum(A)//K+1
B=A*3
SUM=[0]
for a in B:
    SUM.append(SUM[-1]+a)

while NG-OK>1:
    mid=(OK+NG)//2

    flag=0
    for start in range(min(N//K+5,N%K+5)):
        if start>N:
            break
        G=0
        now=start

        for j in range(K):
            now=bisect.bisect_left(SUM,SUM[now]+mid)
            if now>start+N:
                break
        if now<=start+N:
            flag=1
            break

    if flag:
        OK=mid
    else:
        NG=mid
print(OK)