#include <fstream>
using namespace std;

int n, k, sol = 0, s;
int a[1010][1010];
int main()
{
    ifstream f("ferma2.in");
    ofstream g("ferma2.out");

    f >> n >> k;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= i; j++)
            f >> a[i][j], s = s + a[i][j];
    k = n - k;

    for (int i = 1; i <= n - k + 1; i++)
    {
        for (int j = 1; j <= i; j++)
        {
            int l = i, nr = 0;
            for (int jj = j; jj < j + k; jj++)
            {
                for (int ii = l; ii < i + k; ii++)
                    nr += a[ii][jj];
                l++;
            }
            if (sol < s - nr) sol = s - nr;
        }
    }

    g << sol << '\n';
    g.close();
    return 0;
}