<?php
while (1) {
    list($h, $w) = explode(" ", trim(fgets(STDIN)));
    if ($h == 0 && $w == 0) exit;
    for ($i = 0; $i < $h; $i++) {
        echo substr(str_repeat('.#', $w), ($i % 2) ? 0 : 1, $w) . PHP_EOL;
    }
}