def draw(h, w):
    for i in range(h):
        for j in range(w):
            print "#" if (i+j)%2 == 0 else ".",
        print("")
    print("")

while True:
    h, w = map(int, raw_input().split())
    if h == 0 and w == 0:
        break
    draw(h, w)