#include<bits/stdc++.h>
using namespace std;
long long a[1000][1000], sum[1000][1000], sz;
int ans = -1;
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];
			sum[i][j] = sum[i][j - 1] + sum[i - 1][j] - sum[i - 1][j - 1] + a[i][j];
		}
	}
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			for (int l = 1; l <= min(n, m); l++) {
				sz = sum[i + l][j + l] - sum[i + l - 1][j + l] - sum[i + l][j + l - 1] + sum[i + l - 1][j + l - 1];
				if (sz==l*l&&sz!=0&&sz>=ans) {
					ans=sz;
				}
			}
		}
	}
	cout << ans;
	return 0;
}