#include <iostream>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
int main(){
	bool y_stop,x_stop;
	char data[501][501];
	int h,w,x,y,ret;
	while(cin >> h >> w && h || w){
		ret = 0;
		
		rep(i,501)rep(j,501)data[i][j]='*';	

		rep(i,h)rep(j,w)cin >> data[i][j];

		rep(Y,h)rep(X,w){
			y_stop = x_stop = false;
			y = x = 0;
			if(data[Y][X] == '*')continue;
			while(!y_stop || !x_stop){
				if(!y_stop)y++;
				if(!x_stop)x++;
				rep(i,y)if(data[Y+i][X+x]=='*'){x_stop = true;}
				rep(i,x)if(data[Y+y][X+i]=='*'){y_stop = true;}
			}
			//cout << x << " " << y << endl;
			ret = max(x*y,ret);
		}
		cout << ret << endl;
	}
}