#include <cstring>
#include <iostream>
using namespace std;

int main () {
	int w, h;
	while (cin >> h >> w, h || w) {
		int c[h][w];
		for (int i = 0; i < h; i++) {
			char f[w + 1];
			cin >> f;
			for (int j = 0; j < w; j++) {
				if (f[j] == '*') {
					c[i][j] = 0;
				}
				else if (j == 0) {
					c[i][j] = 1;
				}
				else {
					c[i][j] = c[i][j - 1] + 1;
				}
			}
		}
		int ans = 0;
		for (int i = 0; i < h; i++) {
			for (int j = 0; j < w; j++) {
				int minc = c[i][j];
				int s = c[i][j];
				for (int k = 0; i - k >= 0 && c[i - k][j] > 0; k++) {
					minc = min(minc, c[i - k][j]);
					s = max(s, (k + 1) * minc);
				}
				ans = max(ans, s);
			}
		}
		cout << ans << endl;
	}
	return 0;
}