# encoding:utf-8


str_line_1 = '#'
str_line_2 = '.'

def set_char(data):
    if data[len(data)-1] == '#':
        return '.'
    else: return '#'
while True:
    H ,W = map(int, input().split(' '))

    if H == W == 0:
        break

    for i in range(W - 1):
        str_line_1 += set_char(str_line_1)
        str_line_2 += set_char(str_line_2)

    for i in range(H):
        if (i % 2) == 0:
            print(str_line_1)
        else:
            print(str_line_2)