#include <iostream>
#include <algorithm>

#define N 500

using namespace std;

int main()
{
  int h, w;
  char a[N][N];
  int hist[N][N];
  int tmp;

  while(cin>>h>>w && h+w){
    for(int i = 0; i < h; ++i)
      for(int j = 0; j < w; ++j)
     cin >> a[i][j];

    for(int i = 0; i < h; ++i){
      tmp = 0;
      for(int j = w-1; j >= 0; --j){
     if(a[i][j] == '*'){
       tmp = 0;
       hist[i][j] = 0;
     } else {
       hist[i][j] = ++tmp;
     }
      }
    }

    int s = 0, s_max = 0;
    for(int i = 0; i < h; ++i){
      for(int j = 0; j < w; ++j){
     if(a[i][j] == '*') continue;
     s = tmp = hist[i][j];

     for(int k = i+1; k < h; ++k){
       if(a[k][j] == '*') break;
       tmp = min(hist[k][j], tmp);
       s = max(s, (k-i+1)*min(tmp, hist[k][j]));
     }

     s_max = max(s, s_max);
      }
    }

    cout << s_max << endl;
  }

  return 0;
}