#include <bits/stdc++.h>

using namespace std;

int H, W;
int DpOfRow[500][500];

int calculation() {
	int len, ans;

	ans = 0;
	for (int i = 0; i < H; i++) {
		for (int j = W - 1; j > -1; j--) {
			if (DpOfRow[i][j] == 0) {
				continue;
			}
			len = INT_MAX;
			for (int k = i; k < H; k++) {
				len = min(len, DpOfRow[k][j]);
				if (len == 0) {
					break;
				}
				ans = max(ans, len*(k - i + 1));
			}
		}
	}
	
	return ans;
}


int main() {
	char c;

	while (cin >> H >> W, H) {
		memset(DpOfRow, 0, sizeof(DpOfRow));
		for (int i = 0; i < H; i++) {
			for (int j = 0; j < W; j++) {
				cin >> c;
				if (c == '.') {
					DpOfRow[i][j] = (j == 0 ? 1 : DpOfRow[i][j - 1] + 1);
				}
			}
		}
		cout << calculation() << endl;
	}

	return 0;
}
