#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

string map[1000];

int DP[1000][1000];

int main(){
	
	int H, W;
	
	while(true){
		
		cin >> H >> W;
		
		if(H == 0 && W == 0){
			break;
		}
		
		for(int i = 0; i < H; i++){
			cin >> map[i];
		}
		
		int ans = 0;
		
		int count = 0;
		
		for(int i = 0; i < H; i++){
			for(int j = 0; j < W; j++){
				if(map[i][j] == '.'){
					count++;
				}else{
					count = 0;
				}
				DP[i][j] = count;
				if(DP[i][j] > ans){
					ans = DP[i][j];
				}
				//cout << DP[i][j] << " ";
			}
			//cout << endl;
			count = 0;
		}
		//cout << endl;
		
		for(int i = 1; i < H; i++){
			for(int j = 0; j < H - i; j++){
				for(int k = 0; k < W; k++){
					DP[j][k] = min(DP[j][k], DP[j + 1][k]);
					if(DP[j][k] * (i + 1) > ans){
						ans = DP[j][k] * (i + 1);
					}
					//cout << DP[j][k] << " ";
				}
				//cout << endl;
			}
			//cout << endl;
		}
		
		cout << ans << endl;
	}
	return 0;
}