#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <complex>
#include <cstdlib>
#include <cstring>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>

#define mp       make_pair
#define pb       push_back
#define all(x)   (x).begin(),(x).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define repi(i,a,b) for(int i = (a); i < (b); i++)

using namespace std;

typedef    long long          ll;
typedef    unsigned long long ull;
typedef    vector<bool>       vb;
typedef    vector<int>        vi;
typedef    vector<vb>         vvb;
typedef    vector<vi>         vvi;
typedef    pair<int,int>      pii;

const int INF=1<<29;
const double EPS=1e-9;

const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};
int H,W;
char board[520][520];
int dp[520][520];//最大の縦、最大の横
int main(){
	while(cin>>H>>W,H||W){
		for(int i =1;i <=H;i++){
			for(int j =1;j <=W;j++){
				dp[i][j]=0;
			}
		}
		for(int i =1;i <=H;i++){
			int x = 1;
			for(int j =W;j >=1;j--){
				cin>>board[i][j];
				if(board[i][j]=='.'){
					dp[i][j]=x;
					x++;
				}else{
					dp[i][j]=0;
					x = 1;
				}
			}
		}
		int ans = 0;
		for(int i = 1;i <=H;i++){
			for(int j =1;j <= W;j++){
				if(dp[i][j]==0)continue;
				int m =INF;
				for(int k =i;k <=H;k++){
					m =min(m,dp[k][j]);
					if(m==0)break;
					ans =max(ans,(k-i+1)*m);
				}
			}
		}
		cout <<ans<<endl;
	}
	return 0;
}