#include<algorithm>
#include<climits>
#include<cmath>
#include<cstring>
#include<deque>
#include<iomanip>
#include<iostream>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include<utility>
#include<vector>

using namespace std;

using lint = long long;
using P = pair<int, int>;
using LLP = pair<long long, long long>;

#define REP(i, x, n) for(int i = (x), i##_len = int(n) ; i < i##_len ; ++i)
#define rep(i, n) for(int i = 0, i##_len = int(n) ; i < i##_len ; ++i)
#define reps(i, n) for(int i = 1, i##_len = int(n) ; i <= i##_len ; ++i)
#define rrep(i, n) for(int i = int(n) - 1 ; i >= 0 ; --i)
#define rreps(i, n) for(int i = int(n) ; i > 0 ; --i)
#define SORT(x) sort((x).begin(), (x).end())
#define SORT_INV(x) sort((x).rbegin(), (x).rend())
#define TWINS(x) cout << ((x) ? "Yay!" : ":(") << endl

const int IINF = (1 << 30) - 1;
const long long LLINF = 1LL << 61;
const int dx4[] = {1, 0, -1, 0}, dy4[] = {0, 1, 0, -1};
const int dx8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dy8[] = {0, -1, -1, -1, 0, 1, 1, 1};
const double EPS = 1e-8;

template<typename T>
bool chmax(T &_a, T _b){
    if(_a < _b){
        _a = _b;
        return true;
    }else{
        return false;
    }
}

template<typename T>
bool chmin(T &_a, T _b){
    if(_a > _b){
        _a = _b;
        return true;
    }else{
        return false;
    }
}

int max_rectangle(const vector<int> &v){
    int res = 0;
    rep(left, v.size()){
        int mini = v[left];
        REP(right, left, v.size()){
            chmin(mini, v[right]);
            chmax(res, (right - left + 1) * mini);
        }
    }

    return res;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    int h, w;
    while(cin >> h >> w, h){
        vector<string> v(h);
        rep(i, h){
            cin >> v[i];
        }

        vector< vector<int> > t(h, vector<int>(w));
        rep(j, w){
            int cnt = 0;
            rep(i, h){
                if(v[i][j] == '.'){
                    t[i][j] = ++cnt;
                }else{
                    t[i][j] = 0;
                    cnt = 0;
                }
            }
        }

        int ans = 0;
        rep(i, h){
            chmax(ans, max_rectangle(t[i]));
        }

        cout << ans << endl;
    }

    return 0;
}
