#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define ld long double
#define len(v) (int)v.size()
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define pii pair<int, int>
#define vi vector<int>
#define vii vector<vector<int>>
#define vpii vector<pair<int, int>>
#define ull unsigned long long
//#define int long long
//#define ll ull
const int N = 1e6 + 1;
const int maxn = 5e6 + 10;
const int C = 20;
const int logn = 20;
const ll inf = 1e9;
const ll mod = 1e9 + 7;
const int M = 1e9;
const ull M2 = 998244353;
const ld eps = 1e-6;
using namespace std;

template<class T>
istream &operator>>(istream &in, vector<T> &a) {
    for (auto &i : a)
        in >> i;
    return in;
}

template<class T>
ostream &operator<<(ostream &out, vector<T> &a) {
    for (auto &i : a)
        out << i << ' ';
    return out;
}

ll gist(vector<int>& b) {
    int n = len(b);
    vector<pii> s;
    s.emplace_back(0, -1);
    ll res = 0;
    for (int i = 0; i <= n; ++i) {
        int h;
        if (i < n) h = b[i];
        else h = 0;
        int x = i;

        while (h <= s.back().second) {
            x = s.back().first;
            int hprev = s.back().second;
            s.pop_back();
            ll area = 1ll * hprev * (i - x);
            if (area > res) res = area;
        }
        s.emplace_back(x, h);
    }
    return res;
}

void solve() {
    int n, m;
    cin >> n >> m;

    vector<vector<int>> a(n, vector<int>(m));
    for (auto &i: a) {
        for (auto& el : i) {
            int x; cin >> x;
            el = (x ? 0 : 1);
        }
    }
    if (n == 1 && m == 1 && a[0][0] == 1) {
        cout << "1";
        return;
    }
    vector<vector<int>> p(n, vector<int>(m));
    p = a;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            if (p[i][j] && i > 0)
                p[i][j] += p[i - 1][j];
        }
    }
    ll ans = 0;
    for (int i = 0; i < n; ++i) {
        ans = max(ans, gist(p[i]));
    }
    cout << ans;

}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    int T = 1;
    //cin >> T;
    while (T--)
        solve();
}