<?php
$input = trim(fgets(STDIN));
List($h, $w) = explode(" ", $input);

while(($h+$w) > 0) {

  $s1 = str_repeat("#.", ceil($w/2));
  $s2 = strrev($s1);

  for ($i=0; $i<$h; $i++) {
    if (($i % 2) == 0) {
      echo $s1.PHP_EOL;
    } else {
      echo $s2.PHP_EOL;
    }
  }

  echo PHP_EOL;

  $input = trim(fgets(STDIN));
  List($h, $w) = explode(" ", $input);
}