#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repp(i, n) rep(i, 0, n)
#define repb(i, a, b) for(int i = a; i >= b; i--)
#define all(a) a.begin(), a.end()
// #define int long long
using namespace std;

signed main(){
    int h, w;
    while(1){
        cin >> h >> w;
        if(h + w == 0) break;
        string s[510];
        
        rep(i, 0, h) cin >> s[i];
        int d[510][510] = {0};
        
        rep(i, 0, h){
            rep(j, 0, w){
                if(s[i][j] == '*') d[i + 1][j + 1] = 1;
            }
        }
        
        rep(i, 1, h + 1){
            rep(j, 1, w + 1){
                d[i][j] += d[i][j - 1];
            }
        }
        rep(i, 1, w + 1){
            rep(j, 1, h + 1){
                d[j][i] += d[j - 1][i];
            }
        }
        int MAX = 0;
        rep(i, 1, h + 1){
            rep(j, i, h + 1){
                rep(k, 1, w + 1){
                    rep(l, k, w + 1){
                        if(d[j][l] - d[j][k - 1] - d[i - 1][l] + d[i - 1][k - 1] == 0){
                            MAX = max(MAX, (j - i + 1)*(l - k + 1));
                        }
                    }
                }
            }
        }
        cout << MAX << endl;
    }
}