#include<cstdio>
#include<cmath>
#include<algorithm>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<cstdlib>
#include<iomanip>
#include<queue>
#include<set>
#include <valarray>
#include<stack>

using namespace std;

void Solution()
{
    int w,h;
    
    while(cin>>h>>w, h)
    {
        int f[h][w + 1];
        
        for(int i = 0; i < h; i++)
        {
            for(int j = 0; j < w+1; j++)
            {
                if(j == w)
                {
                    f[i][j] = 0;
                    continue;
                }
                
                char t;
                
                cin>>t;
                
                if(i == 0)
                {
                    if(t == '*')
                    {
                        f[i][j]=0;
                    }
                    else
                    {
                        f[i][j]=1;
                    }
                }
                else
                {
                    if(t == '*')
                    {
                        f[i][j] = 0;
                    }
                    else
                    {
                        f[i][j] = f[i - 1][j] + 1;
                    }
                }
            }
        }
        
        int ans = 0;
        
        for(int i = 0; i < h; i++)
        {
            stack<int> pos,height;
            
            for(int j = 0; j < w + 1; j++)
            {
                if(pos.empty())
                {
                    pos.push(j);
                    height.push(f[i][j]);
                }
                else if(height.top()<f[i][j])
                {
                    pos.push(j);
                    height.push(f[i][j]);
                }
                else if(height.top()>f[i][j])
                {
                    int he,p;
                    while(!height.empty() && height.top() > f[i][j])
                    {
                        p=pos.top();
                        pos.pop();
                        
                        he=height.top();
                        height.pop();
                        
                        ans=max(ans,he*(j-p));
                    }
                    
                    height.push(f[i][j]);
                    pos.push(p);
                }
            }
        }
        cout<<ans<<endl;
    }
    
}

int main()
{
    Solution();
    return 0;
}