#include<iostream>
#include<algorithm>
#include<climits>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<ctime>
#include<string>
#include<cstring>
#include<vector>
#include<stack>
#include<queue>
#include<set>
#include<bitset>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;

#define PI 3.141592653589793238462643383279
#define mod 1000000007LL
#define rep(i, n) for(i = 0;i < n;++i)
#define rep1(i, n) for(i = 1;i < n;++i)
#define per(i, n) for(i = n - 1;i > -1;--i)
#define int(x) int x; scanf("%d",&x)
#define int2(x, y) int x, y; scanf("%d%d",&x, &y)
#define int3(x, y, z) int x, y, z; scanf("%d%d%d",&x, &y, &z)
#define int4(v, x, y, z) int v, x, y, z; scanf("%d%d%d%d", &v, &x, &y, &z)
#define int5(v, w, x, y, z) int v, w, x, y, z; scanf("%d%d%d%d%d", &v, &w, &x, &y, &z)
#define ll2(x, y) ll x, y; cin >> x >> y;
#define scn(n, a) rep(i, n)cin >> a[i]
#define sc2n(n, a, b) rep(i, n)cin >> a[i] >> b[i]
#define pri(x) cout << (x) << "\n"
#define pri2(x, y) cout << (x) << " " << (y) << "\n"
#define pri3(x, y, z) cout << (x) << " " << (y) << " " << (z) << "\n"
#define pb push_back
#define mp make_pair
#define all(a) (a).begin(),(a).end()
#define endl "\n"
#define kabe puts("---------------------------")
#define kara puts("")
#define debug(x) cout << " --- " << (x) << "\n"
#define debug2(x, y) cout << " --- " << (x) << " " << (y) << "\n"
#define debug3(x, y, z) cout << " --- " << (x) << " " << (y) << " " << (z) << "\n"
#define X first
#define Y second
#define eps 0.0001
#define prid(x) printf("%.15lf\n", x)

string s;
int sum[501][501];

int getsum(int t, int b, int l, int r){
  return sum[b][r] - sum[b][l - 1] - sum[t - 1][r] + sum[t - 1][l - 1];
}

signed main(void){
  int i, j;
  for(int testcase = 0;testcase >= 0;testcase++){
    int2(h, w);
    if(!(h | w))break;
    rep(i, h + 1)rep(j, w + 1)sum[i][j] = 0;

    rep(i, h){
      cin >> s;
      rep(j, w)if(s[j] == '*')sum[i + 1][j + 1] = 1;
    }

    rep(i, h + 1)rep(j, w)sum[i][j + 1] += sum[i][j];
    rep(i, h)rep(j, w + 1)sum[i + 1][j] += sum[i][j];

    int res = 0;
    rep(i, h)rep(j, i + 1){ // sum:h:[j + 1, i + 1]
      int l = 1, r = 1, tmp;
      for(;;){
        if(r > w)break;
        tmp = getsum(j + 1, i + 1, l, r);
        if(tmp != 0){
          l = ++r;
        }else{
          res = max(res, (i - j + 1) * (r - l + 1));
          ++r;
        }
      }
    }

    pri(res);

//*/

//*/ break;
  }
  return 0;
}