#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <cmath>
#include <map>
#include <queue>
#include <iomanip>
#include <set>
#include <tuple>
#define mkp make_pair
#define mkt make_tuple
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define all(v) v.begin(),v.end()
using namespace std;
typedef long long ll;
const ll MOD=1e9+7;
template<class T> void chmin(T &a,const T &b){if(a>b) a=b;}
template<class T> void chmax(T &a,const T &b){if(a<b) a=b;}

int N,K;
vector<ll> A;

const ll INF=1e15;

bool judge(ll lim){
  int M=A.size();
  vector<vector<int>> to(M,vector<int> (20,M));
  vector<ll> sum(M+1,0);
  rep(i,M) sum[i+1]=sum[i]+A[i];

  int pos=0;
  for(int i=0;i<M;i++){
    while(pos<M&&sum[i]+lim>sum[pos]) pos++;
    to[i][0]=pos;
  }
  for(int k=1;k<20;k++) for(int i=0;i<M;i++){
    if(to[i][k-1]==M) to[i][k]=M;
    else to[i][k]=to[to[i][k-1]][k-1];
  }

  for(int i=0;i<=N-K;i++){
    int now=i;
    for(int k=0;k<20;k++){
      if(K&(1<<k)) now=to[now][k];
      if(now-i>N) break;
    }
    if(now-i<=N) return true;
  }
  return false;
}

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  cin>>N>>K;
  A.resize(N);
  rep(i,N) cin>>A[i];
  
  rep(i,N) A.push_back(A[i]);
  A.push_back(INF);

  ll ok=1,ng=INF;
  while(abs(ok-ng)>1){
    ll mid=(ok+ng)/2;
    if(judge(mid)) ok=mid;
    else ng=mid;
  }

  cout<<ok<<endl;

  return 0;
}