#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

using namespace std;

int main(void){
	int x,y;
	while(cin >> x >> y){
		if(!(x|y)) break;
		vector<string> f(x);
		int table[x][y];
		int tmpi=0;
		int ret=0;
		for(int i=0;i<x;i++) cin >> f[i];
		
		for(int i=0;i<x;i++){
			tmpi = 0;
			for(int j=y-1;j>=0;j--){
				if(f[i][j] == '.'){
					tmpi++;
				}else{
					tmpi = 0;
				}
				table[i][j] = tmpi;
			}
		}
		
		for(int i=0;i<x;i++){
			for(int j=0;j<y;j++){
				if(f[i][j] == '.'){
					int maxiwidth = 1 << 28;
					for(int k=0;k+i<x;k++){
						maxiwidth = min(maxiwidth, table[i+k][j]);
						ret = max(ret, maxiwidth * (k + 1));
					}
				}
			}
		}
		cout << ret << endl;
	}
}