#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;

#define rep(i, n) REP(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define MSG(a) cout << #a << " " << a << endl;
#define REP(i, x, n) for (int i = x; i < n; i++)
#define OP(m) cout << m << endl
typedef long long ll;
typedef unsigned long long ull;

int main()
{
    int w, h;
    while (cin >> h >> w, h)
    {
        int max_area = 0;
        int m[h][w];

        rep(i, h)
        {
            rep(j, w)
            {
                char c;
                cin >> c;
                m[i][j] = (c == '.' ? 1 : 0);
            }
        }
        int a[w + 1] = {};
        a[w] = -1;
        rep(i, h)
        {
            rep(j, w) a[j] = (m[i][j] == 1 ? a[j] + 1 : 0);
            stack<int> st;
            rep(j, w + 1)
            {
                while (!st.empty() && a[st.top()] > a[j])
                {
                    int t = st.top();
                    st.pop();
                    max_area = max(max_area, a[t] * (st.empty() ? j : j - st.top() - 1));
                }
                st.push(j);
            }
        }
        OP(max_area);
    }
    return 0;
}
