#include <iostream>
#include <cstdio>
#include <cstring>
#include <sstream>
#include <algorithm>
#include <math.h>
#include <map>
#include <functional>
#include <iomanip>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <typeinfo>
#define PI 3.14159265359
#define INF 99999999
#define rep(i, n) for(int i=0; i<n; i++)
#define REP(n) rep(i, n)
#define EPS 1e-10
#define pb push_back
#define mp make_pair
typedef long long ll;
using namespace std;
typedef pair<int, int> P;

bool isLeap(int y);
ll gcd(ll a, ll b);
ll lcm(ll a, ll b);
double distanceAB(double xa, double ya, double xb, double yb);
void trace(int A[], int N);

/*
class Target
{
public:
	vector <string> draw(int n)
	{

	}
};
*/


int acc[1024][1001];


int main()
{
	while (1)
	{
		int H, W;
		
		cin >> H >> W;
		if (!H && !W) break;
		rep(i, W) acc[0][i] = 0;
		rep(i, H)
		{
			string line;
			cin >> line;
			rep(c, W)
			{
				if (i > 0) acc[i][c] = acc[i - 1][c];
				if (line[c] == '*') acc[i][c] = 0;
				else acc[i][c]++;
			}
		}
		int ans = 0;
		rep(r, H)
		{
			acc[r][W] = 0;
			stack<pair<int, int> > stk;
			for (int c=0; c<=W; c++)
			{
				int len = 0;
				const int cur = acc[r][c];
				while (!stk.empty() && stk.top().first >= cur)
				{
					len += stk.top().second;
					const int area = len * stk.top().first;
					ans = max(ans, area);
					stk.pop();
				}
				len++;
				stk.push(mp(cur, len));
			}
		}
		cout << ans << endl;
	}
	
	return 0;
}


bool isLeap(int y)
{
	return y % 400 == 0
						? true : y % 100 == 0
						? false : y % 4 == 0
						? true : false;
}

ll gcd(ll a, ll b)
{
	return (b > 0) ? gcd(b, a % b) : a;
}

ll lcm(ll a, ll b)
{
	return a / gcd(a, b) * b;
}

void trace(int A[], int N)
{
	REP(N)
	{
		if (i > 0) cout << " ";
		cout << A[i];
	}
	cout << endl;
}

double distanceAB(double xa, double ya, double xb, double yb)
{
	return sqrt((xb-xa)*(xb-xa) + (yb-ya)*(yb-ya));
}