// Author: btjanaka (Bryon Tjanaka)

// Problem: (UVa) 10074

#include <bits/stdc++.h>

#define GET(x) scanf("%d", &x)

#define GED(x) scanf("%lf", &x)

typedef long long ll;

using namespace std;

typedef pair<int, int> ii;

int a[110][110];

int main() {

int m, n;

while (GET(m) && GET(n) && (m || n)) {

for (int i = 0; i < m; ++i) {

for (int j = 0; j < n; ++j) {

GET(a[i][j]);

if (i > 0) a[i][j] += a[i - 1][j];

if (j > 0) a[i][j] += a[i][j - 1];

if (i > 0 && j > 0) a[i][j] -= a[i - 1][j - 1];

}

}

int mxa = 0;

for (int r0 = 0; r0 < m; ++r0) {

for (int c0 = 0; c0 < n; ++c0) {

for (int r = r0; r < m; ++r) {

for (int c = c0; c < n; ++c) {

int area = a[r][c];

if (r0 > 0) area -= a[r0 - 1][c];

if (c0 > 0) area -= a[r][c0 - 1];

if (r0 > 0 && c0 > 0) area += a[r0 - 1][c0 - 1];

if (area == 0) mxa = max(mxa, (r - r0 + 1) * (c - c0 + 1));

}

}

}

}

printf("%d\n", mxa);

}

return 0;

}