// ?????¬???????????¬??????

#include <iostream>
#include <iomanip>
#include <cstdio>
#include <string>
#include <cstring>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <complex>
#include <cmath>
#include <limits>
#include <cfloat>
#include <climits>
#include <ctime>
#include <cassert>
#include <numeric>
#include <fstream>
#include <functional>
using namespace std;

#define rep(i,a,n) for(int (i)=(a); (i)<(n); (i)++)
#define repq(i,a,n) for(int (i)=(a); (i)<=(n); (i)++)
#define repr(i,a,n) for(int (i)=(a); (i)>=(n); (i)--)
#define int long long int

template<typename T> void chmax(T &a, T b) {a = max(a, b);}
template<typename T> void chmin(T &a, T b) {a = min(a, b);}
template<typename T> void chadd(T &a, T b) {a = a + b;}

typedef pair<int, int> pii;
typedef long long ll;

int dx[] = {0, 0, 1, -1};
int dy[] = {1, -1, 0, 0};
constexpr ll INF = 1001001001001001LL;
constexpr ll MOD = 1000000007LL;

// ?????? N ??????????????°?????????????????¢???????????§
// Verified: AOJ DPL_3_C: Largest Rectangle in a Histogram

int histArea(vector<int> h) {
    // ??????
    int N = h.size();
    h.push_back(0); N++;

    // height, position
    int ans = 0;
    stack<pii> S;
    rep(i,0,N+1) {
        if(S.empty()) S.push(pii(h[i], i));

        if     (S.top().first < h[i])
            S.push(pii(h[i], i));
        else if(S.top().first > h[i]) {
            int lastpos = 0;
            while(!S.empty() && S.top().first >= h[i]) {
                lastpos = S.top().second;
                chmax(ans, S.top().first * (i-lastpos));
                S.pop();
            }
            S.push(pii(h[i], lastpos));
        }
    }
    return ans;
}

// ?????§????????¢?????? (?¶??????????????????????????????£?????§??????????????¢?????¢????????§)
// ??? dp_003_histogram.cpp ????????????????????§??¨??????
// 0 -> ?¶??????????????????? 1 -> ?±??????????????????????
// Verified: AOJ DPL_3_B: Largest Rectangle

int maxRectangle(vector< vector<int> > board) {
    int H = board.size(), W = board[0].size();
    vector< vector<int> > sum(H, vector<int>(W));
    rep(i,0,H) rep(j,0,W) {
        if(board[i][j] == 1) continue;
        sum[i][j] = (i > 0 ? sum[i-1][j] : 0) + 1;
    }
    int ret = 0;
    rep(i,0,H) chmax(ret, histArea(sum[i]));
    return ret;
}

signed main() {
    int H, W;
    while(cin >> H >> W, H || W) {
        char c;
        vector< vector<int> > board(H, vector<int>(W));
        rep(i,0,H) rep(j,0,W) {
            cin >> c;
            if(c == '*') board[i][j] = 1;
            else board[i][j] = 0;
        }
        cout << maxRectangle(board) << endl;
    }
    return 0;
}