#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define ll long long
#define ld long double

using namespace std;
using namespace __gnu_pbds;

typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;

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

const int NMAX = 200;

int n, m;
bool a[NMAX + 1][NMAX + 1];
bool b[NMAX + 1][NMAX + 1];
int prefix_max_area[NMAX + 1];
int suffix_max_area[NMAX + 2];
int v[NMAX + 1];
int st[NMAX + 1], ind_st;
int l[NMAX + 1], r[NMAX + 1];

int get_max_area(int a[], int n) {
    for(int i = 1; i <= n; i++) {
        l[i] = r[i] = 0;
    }

    ind_st = 0;
    for(int i = 1; i <= n; i++) {
        while(ind_st >= 1 && a[st[ind_st]] >= a[i]) {
            ind_st--;
        }
        l[i] = (!ind_st ? 0 : st[ind_st]);
        st[++ind_st] = i;
    }
    
    ind_st = 0;
    for(int i = n; i >= 1; i--) {
        while(ind_st >= 1 && a[st[ind_st]] >= a[i]) {
            ind_st--;
        }
        r[i] = (!ind_st ? n + 1 : st[ind_st]);
        st[++ind_st] = i;
    }

    int max_area = 0;
    for(int i = 1; i <= n; i++) {
        max_area = max(max_area, (r[i] - l[i] - 1) * a[i]);
    }
    return max_area;
}

int get_answer(bool a[NMAX + 1][NMAX + 1], int n, int m) {
    for(int j = 1; j <= m; j++) {
        v[j] = 0;
    }
    for(int i = 0; i <= n; i++) {
        prefix_max_area[i] = 0;
    }
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= m; j++) {
            if(!a[i][j]) {
                v[j]++;
            }
            else {
                v[j] = 0;
            }
        }
        prefix_max_area[i] = max(prefix_max_area[i - 1], get_max_area(v, m));
    }

    for(int j = 1; j <= m; j++) {
        v[j] = 0;
    }
    for(int i = 1; i <= n + 1; i++) {
        suffix_max_area[i] = 0;
    }
    for(int i = n; i >= 1; i--) {
        for(int j = 1; j <= m; j++) {
            if(!a[i][j]) {
                v[j]++;
            }
            else {
                v[j] = 0;
            }
        }
        suffix_max_area[i] = max(suffix_max_area[i + 1], get_max_area(v, m));
    }

    int answer = 0;
    for(int i = 1; i < n; i++) {
        answer = max(answer, prefix_max_area[i] + suffix_max_area[i + 1]);
    }
    return answer;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    fin >> n >> m;
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= m; j++) {
            char x;
            fin >> x;
            a[i][j] = x - '0';
        }
    }

    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= m; j++) {
            b[j][i] = a[i][j];
        }
    }
    fout << max(get_answer(a, n, m), get_answer(b, m, n)) << '\n';
    return 0;
}