#include <cstdio>
#include <iostream>
using namespace std;
int v[1005][1005],w[1005][1005];
int main()
{	
	int n,k,i,j,S=0,Smin=1<<30,nr,r,a;
	freopen("ferma2.in","r", stdin);
	freopen("ferma2.out","w", stdout);
	scanf("%d %d\n",&n,&k);
	for(i=1;i<=n;i++)
		for(j=1;j<=i;j++)
		{
			scanf("%d",&v[i][j]);
			w[i][j]+=w[i-1][j-1]+v[i][j];
			S+=v[i][j];
		}
	for(i=n-k-1;i<=n;i++)
		for(j=1;j+n-k-1<=i;j++)
		{
			nr=0,a=1;
			for(r=j;r<=j+n-k-1;r++)
			{
				nr+=w[i][r]-w[i-a][j-1];
				a++;
			}
			Smin=min(nr,Smin);
		}
	printf("%d",S-Smin);
	return 0;
}