#include <bits/stdc++.h>
using namespace std;
const int N = 110;
int a[N][N], s[N][N];
/*
4 5
1 1 0 0 0
1 0 1 0 0
0 0 0 1 1
0 0 0 1 0
*/
int main() {
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
            cin >> a[i][j];

    // 计算二维前缀和
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
            s[i][j] = s[i - 1][j] + s[i][j - 1] - s[i - 1][j - 1] + a[i][j];

    int res = 0;
    for (int x1 = 1; x1 <= n; x1++)
        for (int y1 = 1; y1 <= m; y1++)
            for (int x2 = x1; x2 <= n; x2++)
                for (int y2 = y1; y2 <= m; y2++) { // 四层循环枚举每个矩形的左上角和右下角
                    if (s[x2][y2] - s[x1 - 1][y2] - s[x2][y1 - 1] + s[x1 - 1][y1 - 1] == 0)
                        res = max(res, (x2 - x1 + 1) * (y2 - y1 + 1));
                }

    cout << res << endl;
    return 0;
}