#include<iostream>

using namespace std;

int H,W;
const int MAX = 500;
const int INF = (1<<20);
int data[MAX][MAX];

int solve(){
  int ans = 0;
  for(int j = 0; j < W; j++)
    for(int i = 0; i < H; i++){
      int able = INF;
      for(int k = i; k < H; k++){
	able = min(able,data[k][j]);
	ans = max(ans,(k-i+1)*able);
      }
    }
  return ans;
}

int main(){
  char c;
  while(cin >> H >> W && H+W){
    for(int i = 0; i < H; i++){
      int now = 0;
      for(int j = 0; j < W; j++){
	cin >> c;
	if(c == '*') data[i][j] = now = 0;
	else data[i][j] = ++now;
      }
    }
    cout << solve() << endl;
  }
  return 0;
}