#include<fstream>
#include<algorithm>
#include<vector>
using namespace std;
ifstream fin("ferma2.in");
ofstream fout("ferma2.out");
int a[1001][1001];
int main()
{
	int n, k, i, c1 = 0, s1, s2, s3, profit=0, x, c2 = 0, c3 = 0, j, f = 0;
	fin >> n >> k;
	for ( i = 1; i <= n; i++ )
		for ( j = 1; j <= i; j++ )
			fin >> a[i][j];
		while ( k )
		{
			s1 = s2 = s3 = 0;
			for ( i = 1+c3+c1; i <= n-c2; i++ )
				s1+= a[i][1+c1];
			for ( i = 1+c1; i <= n-c3-f; i++ )
				s2 += a[n-c2][i];
			for ( i = 1+c1; i <= n-c2; i++ )
				s3 += a[i][i];
			x = max ( s1, max(s2,s3));
			if ( x == s1 )
			{
				profit += s1;
				c1++;
			}
			if ( x == s2 )
			{
				f++;
				profit += s2;
				c2++;
			}
			else
				if ( x == s3) 
				{
					profit += s3;
					c3++;
				}
			k--;
		}
		fout << profit;
	fin.close();
	fout.close();
	return 0;
}