#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <cassert>
#include <iostream>
#include <cctype>
#include <sstream>
#include <string>
#include <list>
#include <vector>
#include <queue>
#include <set>
#include <stack>
#include <map>
#include <utility>
#include <numeric>
#include <algorithm>
#include <iterator>
#include <bitset>
#include <complex>
#include <fstream>
#include <iomanip>
using namespace std;
typedef long long ll;
const double EPS = 1e-9;
typedef vector<int> vint;
typedef pair<int, int> pint;
#define rep(i, n) REP(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define MSG(a) cout << #a << " " << a << endl;
#define REP(i, x, n) for(int i = x; i < n; i++)
template<class T, class C> void chmax(T& a, C b){ if(a < b) a = b; }
template<class T, class C> void chmin(T& a, C b){ if(b < a) a = b; }
template<class T, class C> pair<T, C> mp(T a, C b){ return make_pair(a, b); }

int main()
{
	int H, W;
	while(cin >> H >> W && H)
	{
		vector<string>	field(H);
		vector<vint>	dp(H + 1, vint(W + 1));

		rep(i, H) cin >> field[i];


		rep(i, W + 1) dp[0][i] = i + 1;
		rep(i, H + 1) dp[i][0] = i + 1;

		REP(y, 1, H + 1) REP(x, 1, W + 1)
		{
			dp[y][x] = dp[y-1][x] + dp[y][x-1] - dp[y-1][x-1] + (field[y-1][x-1] == '*');

		}

		//rep(y, H + 1) rep(x, W + 1)
			//cout << dp[y][x] << (x == W ? "\n" : " ");
		
		int size = 0;
		REP(y, 1, H + 1) REP(x, 1, W + 1) rep(sx, x + 1) rep(sy, y + 1)
		{
			if(dp[y][x] - dp[y-sy][x] - dp[y][x-sx] + dp[y-sy][x-sx] == 0)
			{
				chmax(size, sx * sy);
			}
		}


		cout << size << endl;
	}
}