#include <bits/stdc++.h>   using namespace std;   const int MAX = 5009;   string s[MAX];   int n, m, b[MAX], ans, a[MAX];   int main() {     ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);     cin >> n >> m;     for (int i = 0; i < n; i++) cin >> s[i];     for (int i = 0; i < m; i++) {       memset(a, 0, sizeof a);       for (int j = 0; j < n; j++)         if (s[j][i] ==  1 )           b[j]++, a[b[j]]++;         else           b[j] = 0;       for (int i = m; i >= 0; i--) a[i] += a[i + 1], ans = max(ans, a[i] * i);     }     cout << ans;   }   