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:
                if W-1 == 0:
                    print("#")
                    break
                else:
                    print(("#" * int((W-1)/2))+".")
            else:
                print(("." * int((W-1)/2)+"#"))
    print()