#include <iostream>
#include <cmath>

using namespace std;

#define rep(i,b,n) for(int i = b ; i < n ; i++)
const int MAX = 500;

int main(){
  int H,W;

  while(cin >> H >> W , H | W){
    string s[MAX];
    int field[MAX][MAX];

    rep(i,0,H){
      cin >> s[i];
      rep(j,0,W){

	if(s[i][j] == '*') field[i][j] = 0;
	else{
	  if(j > 0) field[i][j] = field[i][j-1] + 1;
	  else field[i][j] = 1;
	}

      }
    }

    int res = 0;

    rep(i,0,W){
      rep(j,0,H){
	int width = 1e9;
        rep(k,j,H){
	  width = min(width,field[k][i]);
	  res = max(res,(k-j+1)*width);
	}
      }
    }

    cout << res << endl;
  }

  return 0;
}