#include<cstdio>
#include<iostream>
int i,j,k,n,m,l,a[52][52],f[52][502][52],max=0,x,s[52][52],sum[52];
int main(){
    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]>max) 
            max=f[i][m][j];
    printf("%d\n",max);
}