#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define all(a)  (a).begin(),(a).end()
#define pb push_back
#define INF (1e9+1)
//#define INF (1LL<<59)

int main(){
	int h,w;
	while(cin>>h>>w&&(h||w)){
		vector<string> fie(h);
		rep(i,h)cin>>fie[i];
		
		vector<vector<int>> dp(h,vector<int>(w,0));
		
		rep(i,h){
			if(fie[i][w-1]=='*')dp[i][w-1]=0;
			else dp[i][w-1]=1;
		}
		rep(i,h){
			for(int j=w-2;j>=0;j--){
				if(fie[i][j]=='*')dp[i][j]=0;
				else dp[i][j] = dp[i][j+1]+1;
			}
		}
		
		
		int maxi = 0;
		rep(i,h){
			rep(j,w){
				int wid = INF;
				rep(k,h){
					if(i+k>=h)continue;
					wid = min(wid,dp[i+k][j]);
					maxi = max<int>(maxi,(k+1)*wid);
				}
			}
		}
		cout<<maxi<<endl;
	}
}