#include<cstdio>
using namespace std;
#define inf 999999999
int n,k,S,smin=inf,s,C[103][103],nr,dif;
int main(){
    freopen("ferma2.in","r",stdin);
    freopen("ferma2.out","w",stdout);
    scanf("%u%u",&n,&k);
    for(int i=1;i<=n;++i){
        for(int j=1;j<=i;++j){
            scanf("%u",&C[i][j]);
            S+=C[i][j];

        }
    }
    dif=n-k;
    for(int i=1;i<=n-dif+1;++i){
        for(int j=1;j<=i;++j){
            s=0; nr=0;

            for(int l=i;l<i+dif;++l){
               // printf("linie: %d  ",l);
                for(int ll=0;ll<=nr;++ll)
                    s+=C[l][j+ll];
                ++nr;
              //  printf("\n");
            }
           // printf("%d\n",s);



            if(s<smin)
                smin=s;
        }
    }
    printf("%u",S-smin);
    return 0;
}