#include <bits/stdc++.h>

using namespace std;

ifstream fin("bmatrix.in");
ofstream fout("bmatrix.out");

const int LMAX = 207;

int dr[LMAX], st[LMAX], sus[LMAX], jos[LMAX], fr[LMAX];
char v[205][205];

int main()
{
    int n, m;
    fin >> n >> m;

    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            fin >> v[i][j];
        }
    }

    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            if (v[i][j] == '0')
            {
                fr[j]++;
            }
            else
            {
                fr[j] = 0;
            }

            int x = INT_MAX;
            int y = 0;

            for (int k = j; k >= 1; k--)
            {
                x = min(x, fr[k]);
                y = max(y, x * (j - k + 1));
            }

            st[i] = max(st[i], max(st[i - 1], y));
            sus[j] = max(sus[j], max(sus[j - 1], y));
        }

    }

    memset(fr, 0, sizeof(fr));

    for (int i = n; i >= 1; i--)
    {
        for (int j = m; j >= 1; j--)
        {
            if (v[i][j] == '0')
            {
                fr[j]++;
            }
            else
            {
                fr[j] = 0;
            }

            int x = INT_MAX;
            int y = 0;

            for (int k = j; k <= m; k++)
            {
                x = min(x, fr[k]);
                y = max(y, x * (k - j + 1));
            }

            dr[i] = max(dr[i], max(dr[i + 1], y));
            jos[j] = max(jos[j], max(jos[j + 1], y));
        }
    }

    int maxim = 0;
    for (int i = 1; i < n; i++)
    {
        maxim = max(maxim, st[i] + dr[i + 1]);
    }
    for (int i = 1; i < m; i++)
    {
        maxim = max(maxim, sus[i] + jos[i + 1]);
    }
    fout << maxim << " ";

    return 0;
}