I missed the last rak'ah of Maghrib prayer, how do I make up my prayer?

If a worshipper misses the last rak'ah of the prayer due to an unintentional reason, such as overcrowding or nosebleed, he must perform a substitute rak'ah after the Imam concludes the prayer with the salām. In this rak'ah, he recites only Al-Fatihah, except in the Fajr or Jumu'ah prayers, in which case he recites Al-Fatihah and an additional surah. He does not perform the prostration of forgetfulness (sujūd as-sahw) because the Imam bears that responsibility. However, if missing the rak'ah was intentional, the prayer is invalid and must be repeated.