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