#include <iostream>
#include <cstdio>
int f[52][52][502];
int a[52][52],s[52][52];
int sum[52];
int maxn(int a,int b){return a>b?a:b;} 
int main(void) {
	freopen("brike.in","r",stdin);
	freopen("brike.out","w",stdout);
	int n,m,max=0;
	int i,j,k,t,l;
	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++)  
             f[i][j][l]=maxn(f[i][j][l],f[i+1][k][l-j]+s[i][j]);
    for(i=1;i<=n;i++)
      for(j=0;j<=n-i+1;j++)
         max=maxn(max,f[i][j][m]);
	printf("%d",max);
	return 0;
}