#!/usr/bin/env python
#-*- coding: utf-8 -*-

import sys

if __name__ == '__main__':
    while 1:
        line = raw_input()
        if line == '0 0':
            break
        a, b = map(int, line.split())
        s0 = ''.join('#' if i % 2 == 0 else '.' for i in range(b))
        s1 = ''.join('.' if i % 2 == 0 else '#' for i in range(b))
        for i in range(a):
            if i % 2 == 0:
                print s0
            else:
                print s1
        print

