TIOJ 1063

// TIOJ 1063
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define SZ(X) (int)(X).size()

bool grid[200][200];
int arr[200];
int n,m;

int solve(){
    vector<int> v;
    int l[200] = {0}, r[200] = {0};
    for(int i = 0; i < m; ++i){
        l[i] = 1;
        while(!v.empty() && arr[i] <= arr[v.back()]){
            l[i] += l[v.back()];
            v.pop_back();
        }
        v.emplace_back(i);
    }
    v.clear();
    for(int i = m-1; i >= 0; --i){
        r[i] = 1;
        while(!v.empty() && arr[i] <= arr[v.back()]){
            r[i] += r[v.back()];
            v.pop_back();
        }
        v.emplace_back(i);
    }

    int ret = 0;
    for(int i = 0; i < m; ++i){
        ret = max(ret, arr[i] * (l[i]+r[i]-1));
    }
    return ret;
}

int32_t main(){
    cin >> n >> m;
    for(int i = 0; i < n; ++i){
        for(int j = 0; j < m; ++j){
            cin >> grid[i][j];
        }
    }
    int ans = 0;
    for(int i = 0; i < n; ++i){
        for(int j = 0; j < m; ++j){
            if(grid[i][j])arr[j] += 1;
            else arr[j] = 0;
        }
        ans = max(ans, solve());
    }
    cout << ans << '\n';
    return 0;
}