#include <bits/stdc++.h>

 using namespace std;

 class Solution

 {

 public:

     int maximalRectangle(vector<vector<char>>& matrix)

     {

         int n = matrix.size(); if (n == ) return ;

         int m = matrix[].size(); if (m == ) return ;

         int ans = ;

         vector<int> h(m, ), l(m, ), r(m, );

         for (int i = ; i < n; i++)

         {

             for (int j = ; j < m; j++)

             {

                 h[j] = (matrix[i][j] == '' ?  : h[j] + );

             }

             stack<int> s;

             for (int j = ; j < m; j++)

             {

                 while (!s.empty() && h[s.top()] >= h[j]) s.pop();

                 l[j] = (s.empty() ?  : s.top() + );

                 s.push(j);

             }

             while (!s.empty()) s.pop();

             for (int j = m - ; j >= ; j--)

             {

                 while (!s.empty() && h[s.top()] >= h[j]) s.pop();

                 r[j] = (s.empty() ? m -  : s.top() - );

                 s.push(j);

             }

             for (int j = ; j < m; j++)

             {

                 ans = max(ans, (r[j] - l[j] + ) * h[j]);

             }

         }

         return ans;

     }

 };

 int main()

 {

     char a[][] = {{'','','','',''},

                   {'','','','',''},

                   {'','','','',''},

                   {'','','','',''}};

     // char a[][4] = {{'1','1','1','1'},

     //               {'1','1','1','1'},

     //               {'1','1','1','1'}};

     vector<vector<char>> v;

     for (int i = ; i < ; i++)

     {

         v.push_back(vector<char>(a[i], a[i] + ));

     }

     cout << Solution().maximalRectangle(v) << endl;

     return ;

 }