#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

#define MAX 501

int main(){
  int H, W;
  char field[MAX][MAX];
  int area[MAX][MAX];

  while(cin >> H >> W){
    if(H == 0 && W == 0) break;
    
    for(int i = 0 ; i < H ; i++){
      for(int j = 0 ; j < W ; j++){
	cin >> field[i][j];
      }
    }

    for(int i = 0 ; i < H ; i++){
      int x = 1;
      for(int j = W-1 ; j >= 0 ; j--){
	if(field[i][j] == '.'){
	  area[i][j] = x;
	  x++;
	}
	else{
	  area[i][j] = 0;
	  x = 1;
	}
      }
    }

    /*for(int i = 0 ; i < H ; i++){
      for(int j = 0 ; j < W ; j++){
	printf("%2d ", area[i][j]);
      }
      cout << endl;
      }*/

    int ans = 0;
    
    for(int i = 0 ; i < H ; i++){
      for(int j = 0 ; j < W ; j++){
	if(i < 0 && area[i][j] == area[i-1][j] || area[i][j] == 0) continue;
	int h = 1;
	int tmp = area[i][j];
	ans = max(ans, h*tmp);
	
	while(i+h < H && area[i+h][j] != 0){
	  tmp = min(tmp, area[i+h][j]);
	  h++;
	  ans = max(ans, h*tmp);
	}
      }
    }

    cout << ans << endl;
  }
}

  