#include <iostream>
#include <vector>

using namespace std;

int H, W;

void solve()
{
    vector<string> map(H);
    int ans = 0;

    for (int i = 0; i < H; i++)
        cin >> map[i];
    
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            if (map[i][j] == '.') {
                int tw = 1, th = 1;
                bool flag = true;

                while (tw + j < W && map[i][tw + j] == '.') 
                    tw++;

                while (i + th < H && flag) {
                    for (int k = 0; k < tw; k++)
                        if (map[i + th][j + k] == '*') {
                            flag = false;
                            break;
                        }
                    if (flag)
                        th++;
                }
                
                if (th * tw > ans)
                    ans = th * tw;
            }
        }
    }
    cout << ans << endl;
}

int main()
{
    while (cin >> H >> W, H || W) {
        solve();
    }

    return 0;
}