while True:
    H, W = map(int, input().split())
    if H == W == 0:
        break
    str = "#." * (W // 2 + 1)
    for i in range(H):
        if i % 2 == 0:
            print(str[:W:])
        else:
            print(str[1:W + 1:])
    print()
