#include <iostream>
#include <stack>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <string>
#include <vector>

#define rep(x,to) for(int x=0;x<to;x++)
#define rep2(x,from,to) for(int x=from;x<to;x++)

using namespace std;


int main(void){

	int h,w;
	string ws;
	while(cin>> h >>w){
		if(h==0 && w==0|| cin.eof()) break;
		vector< vector<int> > ba(h+1,vector<int>(w+1));
		rep(i,h){ 
			cin >> ws;
			rep(j,w){
				if(ws[j] != '*'){
					if(i<1) ba[i][j]=1;
					else ba[i][j] = ba[i-1][j]+1;
				}else{ ba[i][j] = 0; }
			}
		}
		//for(auto x: ba){ for(auto z: x) printf("%d ",z);puts("");}
		int res = 0;
		rep(i,h) rep(j,w){
			int mnh = ba[i][j];
			rep2(k, j+1, w){
				if(ba[i][k]==0) break;
				mnh = min(mnh, ba[i][k]);
				res = max(res, mnh * (k-j+1));
			}
		}
		cout << res << endl;
	}

	return 0;
	
}