h, w = map(int, input().split())
while h != 0 or w != 0:
    l = "#." * (w // 2) + "#" * (w % 2)
    nl = ".#" * (w // 2) + "." * (w % 2)
    for i in range(h):
        print(l)
        l, nl = nl, l
    print()
    h, w = map(int, input().split())

