#include <fstream>

using namespace std;

ifstream cin("ferma2.in");
ofstream cout("ferma2.out");
int a[1002][1002], s[1002][1002];
int main()
{
    int n, k, maxim=0;
    cin>>n>>k;
    for(int i=1;i<=n;++i)
        for(int j=1;j<=i;++j)
            {
                cin>>a[i][j];
                s[i][j]=s[i][j-1]+a[i][j];
                maxim+=a[i][j];
            }
    cin.close();
    int x=n-k, bestSum=(1<<31)-1, sum;
    for(int i=x;i<=n;++i)
        for(int j=x;j<=i;++j)
        {
            sum=0;
            int ii=i;
            int jj=j;
            for(int jj1=1;jj1<=x;++jj1)
            {
                sum+=s[ii][jj]-s[ii][jj-(x-jj1+1)];
                --ii;
                --jj;
            }
            bestSum=min(bestSum, sum);
        }
    cout<<maxim-bestSum<<"\n";
    cout.close();
    return 0;
}