#include<iostream>
#include<string>
#include<algorithm>
#include<map>
#include<set>
#include<utility>
#include<vector>
#include<cmath>
#include<cstring>
#include<cstdio>
#include<time.h>
#define loop(i,a,b) for(int i=a;i<b;i++) 
#define rep(i,a) loop(i,0,a)
#define pb push_back
#define mp make_pair
#define all(in) in.begin(),in.end()
#define it vector<int>::iterator
const double PI=acos(-1);
const double EPS=1e-10;
const int inf=1e8;
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
using namespace std;
int main(){
	int n,m;
	while(cin>>n>>m,n+m){
		vvi in(n,vi(m));
		rep(i,n){
			int co=0;
			rep(j,m){
				char d;
				cin>>d;
				if(d=='.'){
					co++;
					in[i][j]=co;
				}else{
					co=0;
					in[i][j]=0;
				}
			}
		}
		int ma=-1;
		rep(i,n)rep(j,m){
			int t=inf;
			loop(k,i,n){
				t=min(t,in[k][j]);
				if(!t)break;
				ma=max(ma,t*(k-i+1));
			}
		}
		cout<<ma<<endl;
	}
}