#include <bits/stdc++.h>
using namespace std;
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repl(i,0,n)
#define mp(a,b) make_pair((a),(b))
#define pb(a) push_back((a))
#define all(x) (x).begin(),(x).end()
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#define fi first
#define se second
#define dbg(x) cout<<#x" = "<<((x))<<endl
template<class T,class U> ostream& operator<<(ostream& o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream& o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

#define INF 2147483600
#define long long long // for codeforces

int cnt[510][510];

int main(){
  int h,w;
  while(cin>>h>>w, h|w){
    vector<string> vec(h);
    rep(i,h) cin>>vec[i];
    fill(cnt[0], cnt[h], 0);
    rep(j,w) if(vec[0][j]=='.') cnt[0][j]=1;
    repl(i,1,h)rep(j,w){
      if(vec[i][j]=='.') cnt[i][j]=cnt[i-1][j]+1;
    }

    int res=0;
    rep(i,h){
      stack<pair<int,int>> s;
      s.push(mp(-1,-1)); //???????????§?¨?
      rep(j,w+1){
        if(s.top().fi < cnt[i][j]){
          s.push(mp(cnt[i][j], j));
        } else {
          int pos = j;
          while(!s.empty() && cnt[i][j] < s.top().fi){
            auto p = s.top(); s.pop();
            res = max(res, p.fi*(j-p.se));
            pos = p.se;
          }
          s.push(mp(cnt[i][j], pos));
        }
      }
    }
    cout << res << endl;

  }

  return 0;
}