2H  15-18 5422(4 S)/6322/7222
    2S  對成局不太有興趣的relay  通常有4張S
        pass  4522, MIN
        2N    4522, MAX
        3C    2623
        3D    2632
        3H    2722
    2N  問牌型, GF
        3C    2623 or 2632 or 2722, MIN
             (3D=繼續問, then 3H/S/N=2623/2632/2722)
        3D    4522, MIN
        3H    4522, not MIN
        3S    2623, not MIN
        3N    2632, not MIN
        4H    2722, not MIN
    3m  to play
    3H  inv
    3S  inv to 4S/3NT
    3N  to play
    4m  STR m ST
    4H  to play