#include <iostream>
#include <stdio.h>
#include <vector>
#include <string>
#include <algorithm>

using namespace std;

int main(void){
	int w, h;
	while( true ) {
		cin >> h >> w;
		if( w == 0 && h == 0 ) break; 
		vector< string > map( h, "" );
		vector< vector< int > > cntx( h, vector< int > ( w, 0 ) );
		vector< vector< int > > cnty( h, vector< int > ( w, 0 ) );
		vector< vector< int > > sq( h, vector< int > ( w, 0 ) );

		for( int i = 0; i < h; i++ )
			cin >> map[i];
		
		for( int i = w - 1; i >= 0; i-- ) {
			int cnt = 0;
			for( int j = h - 1; j >= 0; j-- ) {
				if( map[j][i] == '*' ) {
					cnt = 0;
					cnty[j][i] = 0;
					continue;
				} else {
					cnt ++;
					cnty[j][i] = cnt;
				}
			}

		}
		
		for( int i = h - 1; i >= 0; i-- ) {
			int cnt = 0;
			for( int j = w - 1; j >= 0; j-- ) {
				if( map[i][j] == '*' ) {
					cntx[i][j] = 0;
					cnt = 0;
					continue;
				} else {
					cnt ++;
					cntx[i][j] = cnt;
				}
			}
		}

		for( int i = 0; i < w; i++ ) {
			for( int j = 0; j < h; j++ ) {
				int min = cnty[j][i];
				for( int k = 0;  k < cntx[j][i] ; k++ ) {
					if( min > cnty[j][i + k] ) {
						min = cnty[j][i + k];
					}
				}
				sq[j][i] = min * cntx[j][i];
			}
		}
		
		int ans = 0;
		for( int i = 0; i < h; i++ )
			for( int j = 0; j < w; j++ )
				if( ans < sq[i][j] ) 
					ans = sq[i][j]; 
		
		/*
		for( int i = 0; i < h; i++ ) {
			for( int j = 0; j < w; j++ ) {
				printf("%3d ", sq[i][j]);
			}
			cout << endl;
		}
		*/
		cout << ans << endl;

	}
    return 0;
}