# include <iostream>
# include <cstdio>
# include <queue>
# include <vector>
# include <stack>
# include <map>
# include <cmath>
# include <algorithm>
# include <stdio.h>
using namespace std;
long long a[100005];
queue <pair<long long,long long> > sums;
vector <int> prev1;
vector <int> suff;
vector <int> sum;
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    freopen ("krasi.out","w",stdout);
    freopen ("krasi.in","r",stdin);
    long long n,m,i,j;
    cin>>n>>m;
    for(i=1; i<=n; i++)
    {
        cin>>a[i];
    }
   int s=0,sums=0;
   for(i=1;i<=n;i++)
   {
       sums+=a[i];
       s+=a[i];
       if(s<0)s=0;
       if(a[i]==0)
       {
           sum.push_back(sums);
           suff.push_back(s);
           s=0;
           for(j=i-1;j>0;j--)
           {
               s+=a[j];
               if(s<0)s=0;
               if(a[j]==0)break;
           }
           prev1.push_back(s);
           sums=0;
           s=0;
       }
   }
   sum.push_back(sums);
   suff.push_back(s);
    s=0;
           for(j=n;j>0;j--)
           {
               s+=a[j];
               if(s<0)s=0;
               if(a[j]==0)break;
           }
           prev1.push_back(s);
           sums=0;
           s=0;
           long long maxsum=0;
for(i=0;i<sum.size();i++)
{

    sums = suff[i];
    //if(sums<0)sums=0;
    for(j=i+1;j<sum.size()&&(j-i)<=m;j++)
    {
        if(sums+prev1[j]>maxsum)maxsum=sums+prev1[j];
        sums+=sum[j];
    }

}
cout<<maxsum<<endl;
}