#include <iostream>
#include <sstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <climits>
#include <cfloat>
using namespace std;

int main()
{
    for(;;){
        int h, w;
        cin >> h >> w;
        if(h == 0)
            return 0;

        vector<string> s(h);
        for(int i=0; i<h; ++i)
            cin >> s[i];

        vector<vector<int> > num(w+1, vector<int>(w+1, 0));
        int ret = 0;
        for(int i=1; i<=h; ++i){
            vector<vector<int> > next(w+1, vector<int>(w+1, 0));
            for(int j=1; j<=w; ++j){
                if(s[i-1][j-1] == '*')
                    continue;
                next[j][1] = num[j][1] + 1;
                ret = max(ret, next[j][1]);
                for(int k=2; k<=j; ++k){
                    next[j][k] = min(num[j][k] + 1, next[j-1][k-1]);
                    ret = max(ret, k * next[j][k]);
                }
            }
            num.swap(next);
        }
        cout << ret << endl;
    }
}