#include<bits/stdc++.h>
using namespace std;
using ll=long long;
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
template<class T> bool chmax(T &a, T b){if (a < b){a = b;return true;} else return false;}
template<class T> bool chmin(T &a, T b){if (a > b){a = b;return true;} else return false;}

const ll INF=1LL<<62;

void Solve(){
    int N,K;
    cin>>N>>K;
    vector<ll>A(N);
    for(int i=0;i<N;i++)cin>>A[i];
    if(K==1){
        ll sum=0,ans=-INF;
        for(int i=0;i<N;i++){
            sum+=A[i];
            chmax(ans,sum);
        }
        cout<<ans<<"\n";
        return;
    }
    ll pf=0,sum=0;
    priority_queue<ll>pq;
    ll ans=-INF;
    for(int i=0;i<N;i++){
        if(pq.size()<K-1){
            pf+=A[i];
            sum+=pf;
            pq.push(pf);
            continue;
        }
        chmax(ans,K*(pf+A[i])-sum);
        pf+=A[i];
        if(pf<pq.top()){
            sum-=pq.top();
            pq.pop();
            pq.push(pf);
            sum+=pf;
        }
    }
    cout<<ans<<"\n";
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    Solve();
}