"use strict"
const input = require('fs').readFileSync('/dev/stdin','utf8');
const arr = input.split('\n')
for (let i in arr) {
	const list = arr[i].split(' ');
	const h = parseInt(list[0]);
	const w = parseInt(list[1]);
	if (h === 0 && w === 0) break;
	printCheeboard(h, w);
	console.log('');
}

function printCheeboard(h, w) {
	let line = '';
	const black = '#';
	const white = '.';
	for (let i = 0; i < h; i++) {
		for (let j = 0 ;j < w; j++) {
			if (isBlack(i, j)) line += black;
			else line += white;
		}
		console.log(line);
		line = '';
	} 
}

function isBlack(i, j) {
	if (i % 2 === 0 && j % 2 === 0) return true;
	if (i % 2 !== 0 && j % 2 !== 0) return true;
	return false;
}
