#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <iomanip>
#include <map>
#include <fstream>
#include <sstream>
#include <math.h>
#include <queue>
#include <stack>

using namespace std;


int main(){
    int H,W;
    char input;
    //入力開始
    while(cin>>H>>W){
        if(H==0&&W==0)break;
        int data[600][600]={0};
        int width[600][600]={0};
        for(int i=0; i<H; i++){
            for(int j=0; j<W; j++){
                cin>>input;
                if(input=='.'){
                    data[i+1][j+1]=1;
                }
            }
        }
        //入力終了
        //処理開始
        /*横の長さを計算*/
        for(int i=1; i<=H; i++){
            for(int j=W; j>=1; j--){
                if(data[i][j]==1){
                    width[i][j]=width[i][j+1]+1;
                }
            }
        }
        int answer = 0;
        
        for(int i=1; i<=H; i++){
            for(int j=1; j<=W; j++){
                if(data[i][j]==1){
                    int min_width = width[i][j];
                    int max_rectangular=width[i][j];
                    for(int k=i+1; k<=H; k++){
                        min_width = min(min_width, width[k][j]);
                        //cout<<min_width<<" ";
                        max_rectangular = max(max_rectangular, min_width*(k-i+1));
                        //cout<<max_rectangular<<endl;
                    }
                    answer = max(answer, max_rectangular);
                }
            }
        }
        cout<<answer<<endl;
        
        
        
        
    }
    
    
}