long long calc(int x)
{
    return f[x - 1] + sum[x + 1];
}
int main()
{
    cin >> n >> k;
    for (int i = 1; i <= n; i++)
        cin >> e[i];
    for (int i = n; i >= 1; i--)
        sum[i] = e[i] + sum[i + 1];
    q.push_back(0);
    for (int i = 1; i <= n; i++) {
        while (!q.empty() && i - q.front() > k)
            q.pop_front();
        while (!q.empty() && calc(q.back()) <= calc(i))
            q.pop_back();
        q.push_back(i);
        f[i] = f[max(q.front() - 1, 0)] + sum[q.front() + 1] - sum[i + 1];
    }
    cout << f[n];
    return 0;
}