const input = require('fs').readFileSync('/dev/stdin', 'utf8').split(/\n/);
const even = '#' + '.';
const odd = '.' + '#';
for (let i = 0; i < input.length; i++) {
    let [a, b] = input[i].split(' ').map(Number);
         if (a === 0 && b === 0) {
        break;
         }
    for (let j = 0; j < a; j++) {
        if (j % 2 === 0) {
        console.log(even.repeat(b).slice(0, b));
        } else {
        console.log(odd.repeat(b).slice(0, b));
        }
    }
    console.log("");
}
