#include <stdio.h>
#define NMax 1010

const char IN[]="ferma2.in",OUT[]="ferma2.out";

int N,K,Rez;
int a[NMax][NMax];
int S[NMax][NMax] , S2[NMax][NMax] , S3[NMax][NMax];
int T[NMax][NMax];

int max(int x,int y){
	return x>y ? x : y;
}

int main()
{
	int i,j,k;
	freopen(IN,"r",stdin);
	scanf("%d%d",&N,&K);
	for (i=1;i<=N;++i) for (j=1;j<=i;++j)
	{
		scanf("%d",&a[i][j]);
		S[i][j]=a[i][j]+S[i-1][j-1];
		S2[i][j]=a[i][j]+S2[i-1][j];
		S3[i][j]=a[i][j]+S3[i][j-1];
	}

	for (i=0;i<=N && i<=K;++i)
	{
		j=K-i;
		for (k=0;k<i;++k)
			T[i][j]+= S3[N-k][N-k];
		for (k=0;k<j;++k)
			T[i][j]+= S2[N-i][k+1];
        Rez=max(Rez,T[i][j]);
	}

	for (k=1;k<=N;++k)
		for (i=0;i<=N;++i)
		{
			j=K-(i+k);
			if (j<0) break;
			T[i][j]= T[i+1][j] + S3[N-i][j] - S3[N-i][N-i-k+1] + /*a[N-i][N-i-k+2] +  a[N-i][N-i-k+3]*/ +S[N-i][N-i-k+1] - S[k+j-1][j] ;
            Rez=max(Rez,T[i][j]);
		}

    freopen(OUT,"w",stdout);
    printf("%d\n",Rez);
    fclose(stdout);
	return 0;
}