import sys
readline=sys.stdin.readline

class Path_Doubling:
    def __init__(self,N,permutation):
        self.N=N
        self.permutation=permutation

    def Build_Next(self,K):
        self.k=K.bit_length()
        self.permutation_doubling=[[self.permutation[n]] for n in range(self.N)]
        for k in range(1,self.k):
            for n in range(self.N):
                self.permutation_doubling[n].append(self.permutation_doubling[self.permutation_doubling[n][k-1]][k-1])

    def Permutation_Doubling(self,N,K):
        for k in range(self.k):
            if K>>k&1:
                N=self.permutation_doubling[N][k]
        return N

def Bisect_Int(ok,ng,is_ok):
    while abs(ok-ng)>1:
        mid=(ok+ng)//2
        if is_ok(mid):
            ok=mid
        else:
            ng=mid
    return ok

N,K=map(int,readline().split())
A=list(map(int,readline().split()))
sum_A=sum(A)
A=[0]+A*2
for i in range(1,2*N+1):
    A[i]+=A[i-1]
def is_ok(ans):
    perm=[i for i in range(2*N+1)]
    r=0
    for l in range(2*N):
        while r<2*N and A[r]-A[l]<ans:
            r+=1
        perm[l]=r
    PD=Path_Doubling(2*N+1,perm)
    PD.Build_Next(K)
    return False
ans=Bisect_Int(0,sum_A//K+1,is_ok)
print(ans)