# -*- coding: utf-8 -*-

a = ['#', '.']

while True:
    n = list(map(int, input().split()))
    if n[0] == 0 & n[1] == 0:
        break

    for i in range(n[0]):
        for j in range(n[1]):
            print('{0}'.format(a[(i + j) % 2]))

        print()

    print()

