#include <cstdio>
#include <algorithm>
#pragma warning(disable : 4996)
int H, W, t, d[507][507], s[507], l[507], r[507]; char c[507][507];
int main() {
	while (scanf("%d%d", &H, &W), H && W) {
		for (int i = 0; i < H; i++) scanf("%s", c[i]);
		for (int i = 0; i < W; i++) {
			for (int j = 0; j < H; j++) {
				if (c[j][i] == '*') d[j][i] = 0;
				else d[j][i] = j ? d[j - 1][i] + 1 : 1;
			}
		}
		int ret = 0;
		for (int i = 0; i < H; i++) {
			t = 0;
			for (int j = 0; j < W; j++) {
				while (t && d[i][s[t - 1]] >= d[i][j]) t--;
				l[j] = t ? (s[t - 1] + 1) : 0;
				s[t++] = j;
			}
			t = 0;
			for (int j = W - 1; j >= 0; j--) {
				while (t && d[i][s[t - 1]] >= d[i][j]) t--;
				r[j] = t ? s[t - 1] : W;
				s[t++] = j;
			}
			for (int j = 0; j < W; j++) ret = std::max(ret, d[i][j] * (r[j] - l[j]));
		}
		printf("%d\n", ret);
	}
}