#include <bits/stdc++.h>
using namespace std;

int n, k;
int a[1000005];

void input() {
    cin >> n >> k;

    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

}

void solve() {
    int zeros = 0;
    int sum = 0;
    int j = 0;
    int ans = 0;

    for (int i = 0; i < n; i++) {
        sum += a[i];
        if (a[i] == 0) zeros++;

        if (sum < 0) {
            sum = 0;
            zeros = 0;
        }

        if (zeros > k) {
            while (zeros > k) {
                if (a[j] == 0) zeros--;
                j++;
            }

            sum = 0;
            i = j - 1;
        }

        if (sum < 0) {
            sum = 0;
            zeros = 0;
        }

        ans = max(sum, ans);
    }

    cout << ans << endl;
}

int main() {
    iostream::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    freopen("krasi.in", "r", stdin);
    freopen("krasi.out", "w", stdout);

    input();
    solve();

    return 0;
}

/*
12 2
1 2 0 0 1 -2 1 1 0 1 2 3
*/