<?php
	while (true) {
		$n = trim(fgets(STDIN));
		list($h, $w) = explode(" ", $n);

		if ($h == 0 && $w == 0) break;

		$ch = ['#', '.'];
		$idx = 0;
		for ($i = 1; $i <= $h; $i++) {
			$idx = ($i % 2 != 0) ? 0 : 1;
			for ($j = 1; $j <= $w; $j++) {
				print $ch[$idx];
				$idx = ($idx) ? 0 : 1;
			}
			print "\n";
		}

		print "\n";
	}