#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define INF (1<<29)

int h, w, dp[500][500];
string str[500];

int main() {
	while (cin >> h >> w, h || w) {
		REP(i, h) cin >> str[i];
		
		fill(dp[0], dp[500], 0);
		
		REP(i, h) REP(j, w) {
			int cnt = 0;
			FOR(k, i, h) {
				if (str[k][j] == '*') break;
				cnt++;
			}
			dp[i][j] = cnt;
		}
		
		int ans = 0;
		REP(i, h) REP(j, w) {
			int tmp = INF;
			FOR(k, j, w) {
				tmp = min(tmp, dp[i][k]);
				if (dp[i][k] == 0) break;
				ans = max(ans, (k - j + 1) * tmp);
			}
		}
		cout << ans << endl;
	}
	return 0;
}