#include <iostream>
#include <string>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;
int m[501][501];
int main()
{
  int h,w;
  while(cin >> h >> w, h){
    memset(m,0,sizeof(m));
    int x,y;
    string s;
    for(y = 1; y <= h; y++){
      cin >> s;
      for(x = 1; x <= w; x++){
	if(s[x-1] == '.') m[y][x] = m[y][x-1]+1;
      }
    }
    int ret = 0;
    for(y=1; y<=h; y++){
      for(x=1; x<=w; x++){
	if(m[y][x] != 0){
	  int j=0, k=m[y][x];
	  for(int i=y; m[i][x] != 0; i++){
	    k = min(k, m[i][x]);
	    j++;
	  }
	  ret = max(ret, j*k);
	}
      }
    }
    cout << ret << endl;
  }
  return 0;
}