#include<cstdio>
#include<queue> 
#define N 1005
#define ls(x) x<<1
#define rs(x) x<<1|1
#define int long long
using namespace std;
int n,m,a[N][N],sum[N][N],t[2][N][N<<2],L[N],R[N],l[N],r[N],ans;
int max(int x,int y){return x>y?x:y;}
void pu(int i,int j,int x){t[i][j][x]=max(t[i][j][ls(x)],t[i][j][rs(x)]);}
void bd(int i,int j,int l,int r,int x)
{
    if(l==r){t[i][j][x]=i?a[l][j]:a[j][l];return;}
    int mid=l+r>>1;
    bd(i,j,l,mid,ls(x));bd(i,j,mid+1,r,rs(x));
    pu(i,j,x);
}
int gs(int i,int j,int l,int r,int sl,int sr,int x)
{
    if(sl<=l&&r<=sr)return t[i][j][x];
    int sum=0,mid=l+r>>1;
    if(sl<=mid)sum=gs(i,j,l,mid,sl,sr,ls(x));
    if(mid<sr)sum+=gs(i,j,mid+1,r,sl,sr,rs(x));
    return sum;
}
inline int d(int x,int y){return x>y?x-y:y-x;}
int read(){
    int sum=0;bool f=0;char c=getchar();
    for(;c<48||c>57;c=getchar())if(c==45)f=1;
    for(;c>=48&&c<=57;c=getchar())sum=sum*10+(c&15);
    return f?-sum:sum;
}
signed main(){
    freopen("zfx.in","r",stdin);freopen("zfx.out","w",stdout);
    n=read();m=read();
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            sum[i][j]=read()+sum[i-1][j]+sum[i][j-1]-sum[i-1][j-1];
    n=n-m+1;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            a[i][j]=sum[i+m-1][j+m-1]+sum[i-1][j-1]-sum[i-1][j+m-1]-sum[i+m-1][j-1];
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            L[i]=max(L[i],a[i][j]),
            R[i]=max(R[i],a[j][i]);
    for(int i=1;i<=n;i++)bd(0,i,1,n,1),bd(1,i,1,n,1);
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            for(int k=1;k<=n;k++)
                for(int l=1;l<=n;l++)
                    if(d(i,k)>=m||d(j,l)>=m)
                        for(int x=1;x<=n;x++)
                            for(int y=1;y<=n;y++)
                                if((d(i,x)>=m||(d(j,y)>=m))&&(d(k,x)>=m||d(l,y)>=m))
                                    ans=max(ans,a[i][j]+a[k][l]+a[x][y]);
    printf("%lld",ans);
    return 0;
}