while True:
    l = input().split()
    h = int(l[0])
    w = int(l[1])
    if h == 0 and w == 0:
        break
    elif h == 1 and w == 1:
        print("#")
        print()
    for i in range(h):
        if i % 2 == 0:
            print("#." * int(w / 2))
        else:
            print(".#" * int(w / 2))
    print()