#include <iostream>
#include <string>
#include <vector>
using namespace std;

bool cells[502][502];
int lft[502][502];

int main() {
    int H, W;
    while (cin >> H >> W, H) {
        char c;
        for (int i=1; i<=H; ++i) {
            for (int j=1; j<=W; ++j) {
                cin >> c;
                cells[i][j] = c == '*';
            }
        }
        for (int i=1; i<=H; ++i) {
            for (int j=1; j<=W; ++j) {
                if (cells[i][j]) {
                    lft[i][j] = 0;
                } else {
                    lft[i][j] = lft[i][j-1] + 1;
                }
            }
        }
        int ans = 0;
        for (int i=1; i<=H; ++i) {
            for (int j=1; j<=W; ++j) {
                int area = 0;
                int wid = 501;
                for (int k=i; k<=H; ++k) {
                    if (cells[k][j]) break;
                    wid = min(wid, lft[k][j]);
                    area = max(area, wid * (k - i + 1));
                }
                ans = max(ans, area);
            }
        }
        cout << ans << endl;
    }
    return 0;
}