while True:
    h, w = [int(s) for s in input().split()]
    if (h + w) == 0:
        break
    
    k = '#.'
    for i in range(h):
        s = k * (w // 2)
        if w % 2 == 1:
            s += k[:1]
        print(s)
        k = k[::-1]
    print()