#line 1 "library/Template/template.hpp"
#include <bits/stdc++.h>
using namespace std;

#define rep(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define ALL(v) (v).begin(),(v).end()
using ll=long long int;
const int inf = 0x3fffffff;
const ll INF = 0x1fffffffffffffff;
template<typename T>inline bool chmax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
template<typename T>inline bool chmin(T& a,T b){if(a>b){a=b;return 1;}return 0;}
#line 2 "library/Utility/fastio.hpp"
#include <unistd.h>

class FastIO{
    static constexpr int L=1<<16;
    char rdbuf[L];
    int rdLeft=0,rdRight=0;
    inline void reload(){
        int len=rdRight-rdLeft;
        memmove(rdbuf,rdbuf+rdLeft,len);
        rdLeft=0,rdRight=len;
        rdRight+=fread(rdbuf+len,1,L-len,stdin);
    }
    inline bool skip(){
        for(;;){
            while(rdLeft!=rdRight and rdbuf[rdLeft]<=' ')rdLeft++;
            if(rdLeft==rdRight){
                reload();
                if(rdLeft==rdRight)return false;
            }
            else break;
        }
        return true;
    }
    template<typename T,enable_if_t<is_integral<T>::value,int> =0>inline bool _read(T& x){
        if(!skip())return false;
        if(rdLeft+20>=rdRight)reload();
        bool neg=false;
        if(rdbuf[rdLeft]=='-'){
            neg=true;
            rdLeft++;
        }
        x=0;
        while(rdbuf[rdLeft]>='0' and rdLeft<rdRight){
            x=x*10+(neg?-(rdbuf[rdLeft++]^48):(rdbuf[rdLeft++]^48));
        }
        return true;
    }
    template<typename T,enable_if_t<is_floating_point<T>::value,int> =0>inline bool _read(T& x){
        if(!skip())return false;
        if(rdLeft+20>=rdRight)reload();
        bool neg=false;
        if(rdbuf[rdLeft]=='-'){
            neg=true;
            rdLeft++;
        }
        x=0;
        while(rdbuf[rdLeft]>='0' and rdbuf[rdLeft]<='9' and rdLeft<rdRight){
            x=x*10+(rdbuf[rdLeft++]^48);
        }
        if(rdbuf[rdLeft]!='.')return true;
        rdLeft++;
        T base=.1;
        while(rdbuf[rdLeft]>='0' and rdbuf[rdLeft]<='9' and rdLeft<rdRight){
            x+=base*(rdbuf[rdLeft++]^48);
            base*=.1;
        }
        if(neg)x=-x;
        return true;
    }
    inline bool _read(char& x){
        if(!skip())return false;
        if(rdLeft+1>=rdRight)reload();
        x=rdbuf[rdLeft++];
        return true;
    }
    inline bool _read(string& x){
        if(!skip())return false;
        for(;;){
            int pos=rdLeft;
            while(pos<rdRight and rdbuf[pos]>' ')pos++;
            x.append(rdbuf+rdLeft,pos-rdLeft);
            if(rdLeft==pos)break;
            rdLeft=pos;
            if(rdLeft==rdRight)reload();
            else break;
        }
        return true;
    }
    template<typename T>inline bool _read(vector<T>& v){
        for(auto& x:v){
            if(!_read(x))return false;
        }
        return true;
    }

    char wtbuf[L],tmp[50];
    int wtRight=0;
    inline void flush(){
        fwrite(wtbuf,1,wtRight,stdout);
        wtRight=0;
    }
    inline void _write(const char& x){
        if(wtRight>L-32)flush();
        wtbuf[wtRight++]=x;
    }
    inline void _write(const string& x){
        for(auto& c:x)_write(c);
    }
    template<typename T,enable_if_t<is_integral<T>::value,int> =0>inline void _write(T x){
        if(wtRight>L-32)flush();
        if(x==0){
            _write('0');
            return;
        }
        else if(x<0){
            _write('-');
            if (__builtin_expect(x == std::numeric_limits<T>::min(), 0)) {
                switch (sizeof(x)) {
                case 2: _write("32768"); return;
                case 4: _write("2147483648"); return;
                case 8: _write("9223372036854775808"); return;
                }
            }
            x=-x;
        }
        int pos=0;
        while(x!=0){
            tmp[pos++]=char((x%10)|48);
            x/=10;
        }
        rep(i,0,pos)wtbuf[wtRight+i]=tmp[pos-1-i];
        wtRight+=pos;
    }
    template<typename T>inline void _write(const vector<T>& v){
        rep(i,0,v.size()){
            if(i)_write(' ');
            _write(v[i]);
        }
    }
public:
    FastIO(){}
    ~FastIO(){flush();}
    inline void read(){}
    template <typename Head, typename... Tail>inline void read(Head& head,Tail&... tail){
        assert(_read(head));
        read(tail...); 
    }
    template<bool ln=true,bool space=false>inline void write(){if(ln)_write('\n');}
    template <bool ln=true,bool space=false,typename Head, typename... Tail>inline void write(const Head& head,const Tail&... tail){
        if(space)_write(' ');
        _write(head);
        write<ln,true>(tail...); 
    }
};

/**
 * @brief Fast IO
 */
#line 3 "sol.cpp"

#line 2 "library/DataStructure/segtree.hpp"

template<typename M,typename N,M (*f)(M,M),M (*g)(M,N),M (*m1)()>struct SegmentTree{
    int n; vector<M> data;
    SegmentTree(int _n=0){
        n=1; while(n<_n)n<<=1; data.assign(2*n,m1());
    }
    void run(vector<M>& v){
        for(int i=0;i<(int)v.size();i++)data[i+n]=v[i];
        for(int k=n-1;k>0;k--)data[k]=f(data[2*k],data[2*k+1]);
    }
    void set(int k,const M &x){
        k+=n; data[k]=x;
        while(k>>=1)data[k]=f(data[2*k],data[2*k+1]);
    }
    void update(int k,const N &x){
        k+=n; data[k]=g(data[k],x);
        while(k>>=1)data[k]=f(data[2*k],data[2*k+1]);
    }
    M query(int a,int b){
        M L=m1(),R=m1();
        for(a+=n,b+=n;a<b;a>>=1,b>>=1){
            if(a&1)L=f(L,data[a++]);
            if(b&1)R=f(data[--b],R);
        }
        return f(L,R);
    }
    M operator[](const int &k)const{return data[k+n];}
};

/**
 * @brief Segment Tree
 */
#line 5 "sol.cpp"

ll f(ll a,ll b){return max(a,b);}
ll g(ll a,ll b){return a+b;}
ll e0(){return -INF;}

FastIO io;
int main(){
    int n,k;
    io.read(n,k);
    vector<int> a(n);
    io.read(a);

    // dp[i][j]:=i番目まで見た時のmax,j:i番目をとったか？
    // dp[i][0]=max(dp[i-1][0],dp[i-1][1])
    // dp[i][1]=max_{i-j<k}dp[j][0]-rui[j]+rui[i]

    vector<ll> tmp(n+1),rui(n+1);
    rep(i,0,n)rui[i+1]=rui[i]+a[i];
    vector dp(n+1,vector<ll>(2));
    SegmentTree<ll,ll,f,g,e0> seg(n+1);
    seg.run(tmp);       

    rep(i,0,n){
        dp[i+1][0]=max(dp[i][0],dp[i][1]);
        dp[i+1][1]=seg.query(max(i-k+2,0),i+1);
        dp[i+1][1]+=rui[i+1];
        seg.update(i+1,dp[i+1][0]-rui[i+1]);
    }
    // io.write(rui);
    ll ret=max(dp[n][0],dp[n][1]);
    io.write(ret);
    return 0;
}