#include <iostream>

using namespace std;

const int N = 500;
const int INF = 1000000000;

int H, W;
char input[N][N];

int solve(){
  int data[N][N];
  for(int i=0;i<H;i++){
    int cnt = 0;
    for(int j=W-1;j>=0;j--){
      if(input[i][j] == '*') cnt = 0;
      else cnt++;
      data[i][j] = cnt;
    }
  }
  /*  for(int i=0;i<H;i++){
    for(int j=0;j<W;j++){
      cout << data[i][j] << ' ' ;
    }
    cout << endl;
    }*/
  int M = -1;
  for(int i=0;i<H;i++){
    for(int j=0;j<W;j++){
      int m = INF;
      for(int k=0;;k++){
	if(i+k >= H || data[i+k][j] == 0) break;
	if(m > data[i+k][j]) m = data[i+k][j];
	if(M < (k+1) * m){
	  M = (k+1) * m;
	  //cout << i << ' ' << j << ' ' << k << ' ' << m << endl;
	}
      }
    }
  }
  return M;
}

main(){
  while(cin >> H >> W){
    if(H == 0 && W == 0) break;
    for(int i=0;i<H;i++){
      for(int j=0;j<W;j++){
	cin >> input[i][j];
      }
    }
    cout << solve() << endl;
  }
  return 0;
}