#include <bits/stdc++.h>
using namespace std;
ifstream in("ferma2.in");
ofstream out("ferma2.out");
int n,k,vert,oriz,diag,a[1005][1005],s[1005][1005],s_diag[1005][1005];
int main()
{int i,j,dif;
    in>>n>>k;
    for (i=1;i<=n;i++)
        for (j=1;j<=i;j++)
            in>>a[i][j];

    ///creez sumele partiale
    for (i=1;i<=n;i++)
        for (j=1;j<=n;j++)
            s[i][j]=a[i][j]+s[i-1][j]+s[i][j-1]-s[i-1][j-1];

    ///creez sumele pe diagonala
    for (dif=0;dif<n;dif++)
        for (j=1;j<=n-dif;j++)
        {
            i=j+dif;
            if (j==1)
                s_diag[i][j]=a[i][j]+s_diag[i][j+1];
            else
                s_diag[i][j]=a[i][j]+s_diag[i-1][j-1]+s_diag[i][j+1]-s_diag[i-1][j];
        }
    for (i=1;i<=n;i++)s_diag[i][0]=s_diag[i][1];

    ///iterez prin toate posibilitatile
    int suma=0,maxim=-1;
    for (vert=0;vert<=k;vert++)
        for (oriz=0;oriz<=k-vert;oriz++)
        {
            diag=k-(oriz+vert);
            suma=0;
            if (vert>0)
            suma+=s[n][vert];
            if (oriz>0)
            suma+=s[n][n]-s[n][vert]-s[n-oriz][n]+s[n-oriz][vert];
            if(diag>0)
            suma+=s_diag[n-oriz][n-oriz-diag+1]-s_diag[vert+diag-1][vert]
                +s[vert+diag-1][n]-s[vert+diag-1][vert];

            maxim=max(maxim,suma);
        }
    out<<maxim<<"\n";
    out.close();
    in.close();
    return 0;
}