How is the Maghrib prayer completed if one joins the congregation in the second rak'ah during the tashahhud?

If you catch the middle Tashahhud in the Maghrib prayer, you follow the Imam and then, after his tasleem, you stand up and pray two rak'ahs. The first rak'ah will be with Al-Fatiha and a surah, and you perform the Tashahhud after its completion. Then you stand for the second rak'ah and recite only Al-Fatiha, perform the final Tashahhud, and give the tasleem. This is based on the principle that what a latecomer catches with the Imam is the beginning of his prayer, and what he performs alone is the end of his prayer, which is the madhhab of Imam Al-Shafi'i. As for someone who catches only one rak'ah of Maghrib, the rak'ah he makes up after the Imam's tasleem will be with Al-Fatiha only, because it is the third (for him). And if the prayer is four rak'ahs and he catches three or two rak'ahs, he must recite only Al-Fatiha in what he makes up, because that is the end of his prayer.