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

int main() {
  int H, W;
  while (cin >> H >> W, H) {
    vector<vector<int>> a(H);
    for (int i = 0; i < H; ++i) {
      a[i].push_back(-1);
      string s; cin >> s;
      for (int j = 0; j < W; ++j) {
        if (s[j] == '*') a[i].push_back(j);
      }
      a[i].push_back(W);
    }
    int ans = 0;
    for (int h1 = 0; h1 < H; ++h1) {
      set<int> st;
      for (int h2 = h1; h2 < H; ++h2) {
        int l = h2 - h1 + 1;
        for (auto&& x : a[h2]) st.insert(x);
        int past = *st.begin();
        for (auto&& now : st) {
          ans = max(ans, l * (now - past - 1));
          past = now;
        }
      }
    }
    cout << ans << endl;
  }
  return 0;
}

