#include <bits/stdc++.h>

using namespace std;
ifstream fin("bmatrix.in");
ofstream fout("bmatrix.out");
const int nmax = 205;
stack < int > stiva;
int n, m, a[nmax], b[nmax], aux[nmax][nmax], maxim, st[nmax], dr[nmax];
char matrix[nmax][nmax];
int Arie(int *v)
{
    while(stiva.size() > 0)
        stiva.pop();
    for(int i = 1; i <= m; ++i)
    {
        while(stiva.size() > 0 && v[i] <= v[stiva.top()])
            stiva.pop();
        if(stiva.size() == 0)
            st[i] = 1;
        else
            st[i] = stiva.top() + 1;
        stiva.push(i);
    }
    while(stiva.size() > 0)
        stiva.pop();
    for(int i = m; i >= 1; i--)
    {
        while(stiva.size() > 0 && v[i] <= v[stiva.top()])
            stiva.pop();
        if(stiva.size() == 0)
            dr[i] = m;
        else
            dr[i] = stiva.top() - 1;
        stiva.push(i);
    }
    int maxx = 0;
    for(int i = 1; i <= m; ++i)
        maxx = max((dr[i] - st[i] + 1)*v[i], maxx);
    return maxx;
}
void solve()
{
    for(int i = 1; i <= max(n, m); ++i)
        a[i] = b[i] = 0;
    for(int i = 1; i <= n; ++i)
    {
        for(int j = 1; j <= m; ++j)
        {
            if(matrix[i][j] == '0')
                aux[i][j] = aux[i - 1][j] + 1;
        }
        a[i] = max(a[i - 1], Arie(aux[i]));
    }
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= m; ++j)
            aux[i][j] = 0;
    for(int i = n; i >= 1; i--)
    {
        for(int j = 1; j <= m; ++j)
            if(matrix[i][j] == '0')
                aux[i][j] = aux[i + 1][j] + 1;
        b[i] = max(b[i + 1], Arie(aux[i]));
    }
    for(int i = 1; i < n; ++i)
        maxim = max(maxim, a[i] + b[i + 1]);
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= m; ++j)
            aux[i][j] = 0;

}
void Rotire()
{
    char k[nmax][nmax];
    for(int j = 1; j <= m; ++j)
    {
        for(int i = 1; i <= n; ++i)
        {
            k[j][i] = matrix[i][j];
        }
    }
    swap(n, m);
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= m; ++j)
            matrix[i][j] = k[i][j];
}
int main()
{
    fin >> n >> m;
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= m; ++j)
            fin >> matrix[i][j];
    solve();
    Rotire();
    solve();
    fout << maxim;
    return 0;
}