while True:
    (H, W) = [int(x) for x in input().split()]

    if H == W == 0:
        break
    if W % 2 == 0:
        for row in range(H):
            if row % 2 == 0:
                print("#." * int(W/2))
            else:
                print(".#" * int(W/2))

    else:
        for row in range(H):
            if row % 2 == 0:
                print(("#." * int((W-1)/2))+"#.")
            else:
                print((".#" * int((W-1)/2)+".#"))
    print()