#include <fstream>

using namespace std;

ifstream f("ferma2.in");
ofstream g("ferma2.out");

int n,k,i,j,st,a[2000][2000],r,s,mini,x,y,ri;

int main () {
    f >> n >> k;
    for (i=1;i<=n;i++)
        for (j=1;j<=i;j++) {
            f >> a[i][j];
            st+=a[i][j];
        }
    r=(n-k)*(n-k+1)/2;
    if (r==0) {
        g << st << '\n';
        f.close();g.close();
        return 0;
    }
    for (i=0;i<=n+1;i++) a[i][0]=a[0][i]=a[n+1][i]=a[i][n+1]=200000;
    mini=st+2;
    for (i=1;i<=n;i++) {
        for (j=1;j<=i;j++) {
            x=i;y=j;s=0;
            for (ri=1;ri<=r;ri++) {
                s+=a[x][y];
                y++;
                if (y-j+1>x-i+1) {y=j;x++;}
            }
            mini=min(mini,s);
            //g << s << ' ';
        }
       // g << '\n';
    }
    g << st-mini << '\n';
    f.close();g.close();
    return 0;
}