#include <bits/stdc++.h>

using namespace std;
ifstream fin("dreptunghi.in");
ofstream fout("dreptunghi.out");
const int nmax = 1000;

int n, m, a[nmax + 5], b[nmax + 5], st[nmax + 5], dr[nmax + 5],aux[nmax + 5][nmax + 5], ans;
bool  matrix[nmax + 5][nmax + 5];
stack < int > S;

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


int Arie(int *v)
{
    while(!S.empty())
        S.pop();
    S.push(0);
    for(int i = 1; i <= m; ++i)
    {
        while(!S.empty() && v[i] <= v[S.top()])
            S.pop();
        if(S.empty())
            st[i] = 1;
        else
            st[i] = S.top() + 1;
        S.push(i);
    }
    while(!S.empty())
        S.pop();
    S.push(m + 1);
    for(int i = m; i >= 1; i--)
    {
        while(!S.empty() && v[i] <= v[S.top()])
            S.pop();
        if(S.empty())
            dr[i] = m;
        else
            dr[i] = S.top() - 1;
        S.push(i);
    }
    int maxx = 0;
    for(int i = 1; i < n; ++i)
        maxx = max(maxx, (dr[i] - st[i] + 1)*v[i]);
    return maxx;
}
void solve()
{
    for(int i = 1; i <= n; ++i)
    {
        for(int j = 1; j <= m; ++j)
            if(matrix[i][j] == 1)
                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 = 1; i <= n; ++i)
        ans = max(ans, a[i]);
    fout << ans;
}
int main()
{
    read();
    solve();
    return 0;
}