#include <bits/stdc++.h>

using namespace std;

int main() {
    cin.tie(NULL);
    ios::sync_with_stdio(false);
        freopen("krasi.in", "r", stdin);
    #ifndef LOCAL
        freopen("krasi.out", "w", stdout);
    #endif

    int N,K;
    cin>>N>>K;
    vector<int> a(N);
    for(int i=0;i<N;i++)cin>>a[i];

    int curz=0;
    int best = INT_MIN;

    int l=0;
    for(int l=0;l<N;) {
        int r=l,curz=0;
        while(r<N && curz<=K) {
            if(a[r++]==0)curz++;
        }
        //cout<<"try"<<l<<" "<<r<<endl;
        int sum = 0;
        for(int i=l;i<r;i++) {
            sum = max(sum+a[i],a[i]);
            best = max(best,sum);
        }
        while(l<N && a[l]!=0)l++;
        l++;
    }
    cout<<best<<endl;

    return 0;
}