#include <bits/stdc++.h>
using namespace std;
 
int n, k;
int a[1005][1005];
 
void init() {
    cin >> n >> k;
 
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> a[i][j];
        }
    }
 
 
 
 
}
 
void solve() {
    long long lonNhat = 0;
 
    for (int i = 0; i <= n - k; i++) {
        for (int j = 0; j <= n - k; j++) {
            long long tong = 0;
 
            for (int u = i; u < i + k; u++) {
                for (int v = j; v < j + k; v++) {
                    tong += a[u][v];
                }
            }
 
            if (tong > lonNhat)
                lonNhat = tong;
        }
    }
 
    cout << lonNhat;
}
 
int main() {
    init();
    solve();
    return 0;
}
 
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