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

#define rep(i,x,y) for(int i=(x);i<(y);++i)
#define debug(x) #x << "=" << (x)

#ifdef DEBUG
#define _GLIBCXX_DEBUG
#define dump(x) std::cerr << debug(x) << " (L:" << __LINE__ << ")" << std::endl
#else
#define dump(x)
#endif

typedef long long int ll;
typedef pair<int,int> pii;
//template<typename T> using vec=std::vector<T>;

const int inf=1<<30;
const long long int infll=1LL<<58;
const double eps=1e-9;
const int dx[]={1,0,-1,0},dy[]={0,1,0,-1};

template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec){
	os << "[";
	for (const auto &v : vec) {
		os << v << ",";
	}
	os << "]";
	return os;
}

void solve(){
    int h,w;
    while(cin >> h >> w){
        if(h==0 and w==0) break;

        vector<vector<char>> c(h,vector<char>(w));
        rep(y,0,h) rep(x,0,w) cin >> c[y][x];

        vector<vector<int>> s(h,vector<int>(w));
        rep(y,0,h) rep(x,0,w){
            if(c[y][x]=='.'){
                s[y][x]=1;
                if(y!=0) s[y][x]+=s[y-1][x];
            }
        }

        int ans=0;
        rep(y,0,h){
            vector<int>& v=s[y];
            stack<pii> stk;
            rep(x,0,w){
                int pos=x;
                while(!stk.empty() and v[x]<stk.top().first){
                    ans=max(ans,(x-stk.top().second)*stk.top().first);
                    pos=stk.top().second;
                    stk.pop();
                }
                if(stk.empty() or v[x]>stk.top().first) stk.push(make_pair(v[x],pos));
            }
            while(!stk.empty()){
                ans=max(ans,(w-stk.top().second)*stk.top().first);
                stk.pop();
            }
        }
        cout << ans << endl;
    }
}

int main(){
	std::ios::sync_with_stdio(false);
	std::cin.tie(0);
	solve();
	return 0;
}