# coding:utf-8
import sys
while True:
    array = map(int, raw_input().split())
    if array[0] == 0 and array[1] == 0:
        break
    for i in range(array[0]):
        for j in range(array[1]):
            if i % 2 == 0 and j % 2 == 0:
                sys.stdout.write('#')
            elif i % 2 == 1 and j % 2 == 0:
                sys.stdout.write('.')
            elif i % 2 == 0 and j % 2 == 1:
                sys.stdout.write('.')
            else:
                sys.stdout.write('#')
        else:
            print
    else:
        print

