#include<iostream>
using namespace std;
#define REP(i,b,n) for(int i=b;i<n;i++)
#define rep(i,n)   REP(i,0,n)
#define N 500
int w[N][N];
char m[N][N+1];

int sol(int r,int c){
  rep(i,r){
    w[i][0]=m[i][0]=='.'?1:0;
    REP(j,1,c)w[i][j]=m[i][j]=='*'?0:w[i][j-1]+1;
  }
  int ret=0,mw;
  rep(j,c){
    rep(i,r){
      ret=max(ret,mw=w[i][j]);
      REP(k,i+1,r&&mw){
	mw=min(mw,w[k][j]);
	ret=max(ret,(k-i+1)*mw);
      }
    }
  }
  return ret;
}

main(){
  int r,c;
  while(cin>>r>>c && r){
    rep(i,r)cin>>m[i];
    cout<<sol(r,c)<<endl;
  }
}