# include <fstream>
 
 # define dim 1005
 
 using namespace std;
 
 ifstream f("ferma2.in");
 ofstream g("ferma2.out");
 
 int a[ dim ][ dim ];
 int suma;
 int n, k;
 int nr, sumamaxima;
 
 void citire()
 {
	 int i, j;
	 f >> n >> k;
	 for ( i = 1 ; i <= n ; i++ )
		 for ( j = 1 ; j <= i ; j++ )
		 {
			 f >> a[ i ][ j ];
			 suma = suma + a[ i ][ j ];
		 }
		 
		 /*for ( i = 1 ; i <= n ; i ++ )
		 {
			 for ( j = 1 ; j <= n ; j++ )
				 g << a[ i ][ j ] << " ";
			 g << "\n";
		 }*/
 }
 
 void rezolva()
 {
	 int i, j, p, sumac = 0;
	 nr = n - k;
	 for ( i = n ; i >= nr ; i-- )
	 {
		 for ( j = i - nr + 1 ; j >= 1 ; j-- )
		 {
			 sumac = a[ i ][ j ];
			 for( p = 1 ; p < nr ; p++ )
				 sumac = sumac + a[ i - p ][ j ] + a[ i ][ p + j ];
	
			 if ( sumamaxima < suma - sumac )
				 sumamaxima = suma - sumac;
		 } 
		 
	 }
	 
	 g << sumamaxima;
 }
 
 int main()
 {
	 citire();
	 rezolva();
	 return 0;
 }