#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
deque <int> q,q2;
int v[10002];
int main()
{
    ifstream fin ("ferma.in");
    ofstream fout ("ferma.out");
    int nr=0,k,i,n,pp=0;
    long long sum=0,maxc=0;
    fin>>n>>k;
    for(i=1; i<=n; i++)
        fin>>v[i];
    for(i=1; i<=n; i++)
        v[n+i]=v[i];
    for(i=1; i<=2*n&&pp==0; i++)
    {
        sum=sum+v[i];
        if(i>n&&(sum<0||v[i]<0))
            pp=1;
        else
        {
            if(sum>0)
            {
                if(sum>maxc)
                    maxc=sum;
            }
            else
            {
                if(maxc>0)
                {
                    nr++;
                    while(!q.empty()&&q.back()>=maxc)
                    {
                        q.pop_back();
                        q2.pop_back();
                    }
                    q.push_back(maxc);
                    q2.push_back(nr);
                    if(nr>=k)
                        if(q.front()<nr-k+1)
                        {
                            q.pop_front();
                            q2.pop_front();
                        }
                }
                sum=0;
                maxc=-1;
            }
        }
    }
    if(maxc>0)
    {
        nr++;
        while(!q.empty()&&q.back()>=maxc)
        {
            q.pop_back();
            q2.pop_back();
        }
        q.push_back(maxc);
        q2.push_back(nr);
        if(nr>=k)
            if(q2.front()<nr-k+1)
            {
                q.pop_front();
                q2.pop_front();
            }
    }
    sum=0;
    while(!q.empty())
    {
        sum+=q.front();
        q.pop_front();
    }
    fout<<sum;
    return 0;
}