#include<iostream>
using namespace std;

int main()
{
  int h,w;
  for(;cin>>h>>w,h||w;)
    {
      char maps[h][w];
      int tate[h][w];
      for(int i=0;i<h;i++)
	for(int j=0;j<w;j++)
	  {
	    cin>>maps[i][j];
	    if(maps[i][j]=='*')
	      {
		tate[i][j]=0;
	      }
	    else
	      {
		if(i==0)
		  tate[i][j]=1;
		else
		  tate[i][j]=tate[i-1][j]+1;
	      }
	  }
      //      cout<<endl;
      int ans=0;
      for(int i=h-1;i>0;i--)
	{
	  int cnt=0;
	  int min_tate=99999;
	  for(int j=w-1;j>=0;j--)
	    {
	      if(tate[i][j]!=0)
		{
		  min_tate=min(min_tate,tate[i][j]);
		  cnt++;
		  ans=max(ans,min_tate*cnt);
		  //	  cout<<ans<<endl;
		}
	      else
		{
		  cnt=0;
		  min_tate=99999;
		}
	      //cout<<tate[i][j];
	    }
	}
      cout<<ans<<endl;

    }

}