#include<cstdio>

#include<cstdlib>

const int N=20010,inf=1000000000;

int n,k,i,l,r,mid,ans0,ans1,f,sum[N];

inline int max(int a,int b){return a>b?a:b;}

inline int min(int a,int b){return a<b?a:b;}

struct node{

  int p,val,vmx,vmi,mx,mi;node*l,*r;

  node(){val=p=0,vmx=mx=-inf,vmi=mi=inf;l=r=NULL;}

  inline void up(){

    mx=max(vmx,max(l->mx,r->mx));

    mi=min(vmi,min(l->mi,r->mi));

  }

}*blank=new(node),pool[N],*cur=pool,*T;

inline void Rotatel(node*&x){node*y=x->r;x->r=y->l;x->up();y->l=x;y->up();x=y;}

inline void Rotater(node*&x){node*y=x->l;x->l=y->r;x->up();y->r=x;y->up();x=y;}

void Ins(node*&x,int p,int v){

  if(x==blank){

    x=cur++;x->val=p;x->l=x->r=blank;x->vmx=x->mx=x->vmi=x->mi=v;x->p=std::rand();

    return;

  }

  x->mx=max(x->mx,v);

  x->mi=min(x->mi,v);

  if(p==x->val){

    x->vmx=max(x->vmx,v);

    x->vmi=min(x->vmi,v);

    return;

  }

  if(p<x->val){

    Ins(x->l,p,v);

    if(x->l->p>x->p)Rotater(x);

  }else{

    Ins(x->r,p,v);

    if(x->r->p>x->p)Rotatel(x);

  }

}

int Askmx(node*&x,int p){

  if(x==blank)return -inf;

  if(p==x->val)return max(x->vmx,x->r->mx);

  if(p<x->val)return max(x->vmx,max(x->r->mx,Askmx(x->l,p)));

  return Askmx(x->r,p);

}

int Askmi(node*&x,int p){

  if(x==blank)return inf;

  if(p==x->val)return min(x->vmi,x->r->mi);

  if(p<x->val)return min(x->vmi,min(x->r->mi,Askmi(x->l,p)));

  return Askmi(x->r,p);

}

int main(){

  blank->l=blank->r=blank;

  scanf("%d%d",&n,&k);

  for(i=1;i<=n;i++)scanf("%d",&sum[i]),sum[i]+=sum[i-1];

  l=-inf,r=ans0=ans1=inf;

  while(l<=r){

    mid=(l+r)>>1;

    cur=pool,Ins(T=blank,0,0);

    for(i=1;i<=n;i++)Ins(T,sum[i],f=Askmx(T,sum[i]-mid)+1);

    if(f>=k)r=(ans0=mid)-1;else l=mid+1;

  }

  l=-inf,r=inf;

  while(l<=r){

    mid=(l+r)>>1;

    cur=pool,Ins(T=blank,0,0);

    for(i=1;i<=n;i++)Ins(T,sum[i],f=Askmi(T,sum[i]-mid)+1);

    if(f<=k)r=(ans1=mid)-1;else l=mid+1;

  }

  return printf("%d",max(ans0,ans1)),0;

}