#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return true; } return false; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return true; } return false; }
#define vi vector<int>
#define vl vector<ll>
#define vii vector<pair<int,int>>
#define vll vector<pair<ll,ll>>
#define vvi vector<vector<int>>
#define vvl vector<vector<ll>>
#define vvii vector<vector<pair<int,int>>>
#define vvll vector<vector<pair<ll,ll>>>
#define vst vector<string>
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define mkunique(x) sort(all(x));(x).erase(unique(all(x)),(x).end())
#define fi first
#define se second
#define mp make_pair
#define si(x) int(x.size())
const int mod=998244353,MAX=300005,INF=15<<26;

int main(){
    
    std::ifstream in("text.txt");
    std::cin.rdbuf(in.rdbuf());
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    ll N,K;cin>>N>>K;
    vl S(N);
    for(int i=0;i<N;i++){
        cin>>S[i];
    }
    for(int i=N-2;i>=0;i--) S[i]+=S[i+1];
    ll ans=-(15LL<<58);
    priority_queue<ll,vector<ll>,greater<ll>> PQ;
    ll sum=S[0];
    if(si(PQ)==K-1&&0+1<N) chmax(ans,sum-S[0+1]*K);
    if(si(PQ)==K-1) chmax(ans,sum);
    for(int i=1;i<N;i++){
        sum+=S[i];
        PQ.push(S[i]);
        if(si(PQ)>K-1){
            sum-=PQ.top();PQ.pop();
        }
        if(si(PQ)==K-1&&i+1<N) chmax(ans,sum-S[i+1]*K);
        if(si(PQ)==K-1) chmax(ans,sum);
    }
    cout<<ans<<"\n";
    
}