<?php  //?????§??? tamesi
while (true) {
    list($height, $width) = getInputExplodeBySpaces();
    
    if ($height == 0 && $width == 0) {
       break;
    }
    
    $chessBoardRectangle = new ChessBoardRectangle($height, $width);
    echo $chessBoardRectangle->makeChessBoardRectangle(), PHP_EOL;
}
 
function getInputExplodeBySpaces()
{
    return explode(' ', trim(fgets(STDIN)));
}
  
class Rectangle
{
    public $height;
    public $width;
    public $hashSymbol  = '#';
    
    public function __construct($height, $width)
    {
        $this->height = $height;
        $this->width  = $width;
    }

    public function setRectangleParts()
    {
        for ($i = 0; $i < $this->height; $i++) {
            for($j = 0; $j < $this->width; $j++) {
                $rectangleParts[$i][$j] = $this->hashSymbol;
            }
        }
        return $rectangleParts;
    }
    
    public function mergeRectangleParts($rectangleParts)
    {
        for ($i = 0; $i < $this->height; $i++) {
            $lines[] = implode($rectangleParts[$i]).PHP_EOL;
        }
        return implode($lines).PHP_EOL;
    }
}
 
class FrameRectangle extends Rectangle
{
    public $dotSymbol = '.';
    
    public function makeFrameRectangle()
    {
        $lines = $this->setRectangleParts();
        for ($i = 1; $i < $this->height - 1; $i++) {
            for($j = 1; $j < $this->width - 1; $j++) {
                $lines[$i][$j] = $this->dotSymbol; 
            }
        }
        
        return $this->mergeRectangleParts($lines);
    }
}

class ChessBoardRectangle extends FrameRectangle
{
    public function makeChessBoardRectangle()
    {
        $lines = $this->setRectangleParts();
        for ($i = 0; $i < $this->height; $i++) {
            for ($j = 0; $j < $this->width; $j++) {
                if ($j % 2 == 0 && $i % 2 ) {
                    $lines[$i][$j] = $this->dotSymbol;
                } elseif ($j % 2 && $i % 2 == 0) {
                    $lines[$i][$j] = $this->dotSymbol;
                }
            }
        }
        
        return $this->mergeRectangleParts($lines);
    }
}