#include<bits/stdc++.h>
using namespace std;
long long n;
long long A[100005];
long long otg[100005];
long long nuli[100005];
long long sbor[100005];
multiset<long long>s;
int main(){
freopen("krasi.in","r",stdin);
freopen("krasi.out","w",stdout);
long long n,k;
cin>>n>>k;
for(long long i=0; i<n; i++)
{
    cin>>A[i];
    if(i==0){sbor[i] = A[i]; continue;}
    nuli[i]=nuli[i-1];
    if(A[i]==0)
        nuli[i]++;
    sbor[i] = sbor[i-1]+A[i];
}
long long l = -1;
for(long long i=0; i<n; i++)
{
    if(nuli[i]> k) {
        for(long long j=max(0ll,l); j<i; j++)
        {
            if(nuli[i]-nuli[j]<=k)
            {
                l = j;
                break;
            }
            auto it = s.find(sbor[j]);
            if(it!=s.end())
            {
                s.erase(it);
            }
        }
    }

    otg[i] = sbor[i];
    if(l>=0 ) otg[i] -= sbor[l];
    //cout<<i<<" "<<otg[i]<<endl;
    auto it = s.begin();
    if(!s.empty())
    {
        if(!s.empty() && otg[i]-((*it)-sbor[l])>otg[i])
        {
            otg [i]  = otg[i]-((*it)-sbor[l]);//(*it);
            //cout<<"maham "<<(*it)<<endl;
        }
    }
    s.insert(sbor[i]);

}
/*
for(long long i=0; i<n; i++)
    cout<<sbor[i]<<" "; cout<<endl;
for(long long i=0; i<n; i++)
    cout<<otg[i]<<" "; cout<<endl;*/
long long maxx = otg[0];
for(long long i=1; i<n; i++)
    maxx = max(maxx, otg[i]);
cout<<maxx<<endl;
return 0;
}