#include<stdio.h>
#include<assert.h>
#include<algorithm>
using namespace std;

int n,k,l,s,sm,a[1001][1001],diag[1001][1001],col[1001][1001],line[1001][1001],diag2[1001][1001];

void read()
{
    assert(freopen("ferma2.in","r",stdin)!=NULL);
    int i,j;
    scanf("%d%d",&n,&k);
    for(i=1;i<=n;++i)
        for(j=1;j<=i;++j)
        {
            scanf("%d",&a[i][j]);
            diag[i][j]=a[i][j]+diag[i-1][j-1]+diag[i][j+1];
            diag2[i][j]=a[i][j]+diag2[i-1][j-1]+diag[i-1][j];
            line[i][j]=a[i][j]+line[i][j-1]+line[i-1][j];
            col[i][j]=a[i][j]+col[i-1][j]+col[i][j-1];
        }
}

inline int valid(int x,int y)
{
    return (x-y+1)>=l;
}

inline int val(int x,int y)
{
    int z;
    z=0;
    z+=diag[n][y+l];
    z+=col[n][y-1];
    z+=line[n][n]-line[x][x];
    z-=col[x][y-1];
    z-=diag2[x+l][y];
    z-=diag[n][y+l]-diag[x][y+l];
    return sm-z;
}

void solve()
{
    int i,j;
    l=n-k;
    for(i=1;i<=n;++i)
        for(j=1;j<=i;++j)
            sm+=a[i][j];
    if(l==0)
    {
        s=sm;
        return;
    }
    for(i=1;i<=n;++i)
        for(j=1;j<=i;++j)
            if(valid(i,j))
                s=max(s,val(i,j));
}

void write()
{
    assert(freopen("ferma2.out","w",stdout)!=NULL);
    printf("%d",s);
}

int main()
{
    read();
    solve();
    write();
    return 0;
}