#include<cstdio>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<algorithm>
using namespace std;
int i,j,k,n,m,l;
int a[52][52];
int f[52][502][52];
int maxx,x;
int s[52][52];
int sum[52];
int main(){
	freopen("brike.in","r",stdin);
	freopen("brike.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(i=1;i<=n;i++)
      	for(j=1;j<=n-i+1;j++){
        	scanf("%d",&a[i][j]);
        	s[j][i]=s[j][i-1]+a[i][j];
      	}
    for(i=1;i<=n;i++)
      	sum[i]=sum[i-1]+i;
    f[n+1][0][0]=0;
    for(i=n;i>=1;i--)
      	for(j=0;j<=n-i+1;j++)
        	for(k=j-1;k<=n-i;k++)
          		for(l=j+sum[k];l<=m;l++)
            		if(f[i][l][j]<f[i+1][l-j][k]+s[i][j])
						f[i][l][j]=f[i+1][l-j][k]+s[i][j];
    for(i=1;i<=n;i++)
      	for(j=0;j<=n-i+1;j++)
        	if(f[i][m][j]>maxx)
            	maxx=f[i][m][j];
    printf("%d\n",maxx);
    return 0;
}