#include<bits/stdc++.h>
using namespace std;
#define el "\n"
#define ll long long
#define ull unsigned long long
#define se second
#define fi first
#define be begin()
#define en end()
#define Faster cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(0);
int main()
{
    Faster;
    int n, m; cin >> n >> m;
    int a[n][m];
    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < m; j++)
        {
            cin >> a[i][j];
        }
    }
    int ans = INT_MIN;
    for(int i = 0; i < n - 1; i++)
    {
        for(int j = 0; j < m - 1; j++)
        {
            int tmp = 0;
            for(int x = i; x < i + 2; x++)
            {
                for(int y = j; y < j + 2; y++)
                {
                    tmp += a[x][y];
                }
            }
            ans = max(ans, tmp);
        }
    }
    cout << ans;
}
 

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0 0 1 1 0