#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1010;
int n,m,a[N][N],mk[N][N];
ll ans;
void dfs (int idx,ll sum) {
    //cout << sum <<endl;
    if (idx>3) {
        ans=max(ans,sum);
        return;
    }
    for (int i=1;i<=n;i++) {
        for (int j=1;j<=n;j++) {
            if (mk[i][j]||i+m-1>n||j+m-1>n) continue;
            ll t=0;
            for (int l=i;l<=i+m-1;l++) {
                for (int r=j;r<=j+m-1;r++) {
                    mk[l][r]=1;
                    t+=a[l][r];
                }
            }
            dfs(idx+1,sum+t);
            for (int l=i;l<=i+m-1;l++) {
                for (int r=j;r<=j+m-1;r++) {
                    mk[l][r]=0;
                }
            }
        }
    }
}
int main () {
    freopen("zfx.in","r",stdin);
    freopen("zfx.out","w",stdout);
    ios::sync_with_stdio(0);
    cin.tie(0),cout.tie(0);
    cin >> n >> m;
    for (int i=1;i<=n;i++) {
        for (int j=1;j<=n;j++) {
            cin >> a[i][j];
        }
    }
    dfs(1,0);
    cout << ans <<endl;
    return 0;
}