#include<fstream>
using namespace std;
ifstream f("ferma2.in");
ofstream g("ferma2.out");
int n,k,i,j,ii,jj,maxi,mini,sum,jj1,a[1001][1001],s[1001][1001];
int main()
{f>>n>>k;
for(i=1;i<=n;++i)
	for(j=1;j<=i;++j)
		f>>a[i][j];
for(i=1;i<=n;++i)
	for(j=1;j<=i;++j)
		s[i][j]=s[i][j-1]+a[i][j],maxi+=a[i][j];
mini=maxi+1;
for(i=n-k;i<=n;++i)
	for(j=n-k;j<=i;++j)
	{sum=0;
	ii=i;
	jj=j;
	for(jj1=1;jj1<=n-k;++jj1)
	{sum+=s[ii][jj]-s[ii][jj-(n-k-jj1+1)];
	--ii;
	--jj;
	}
	if(mini>sum)
		mini=sum;
	}
g<<maxi-mini<<'\n';
return 0;
}