10373
The earliest was that of the famous Al-Ma ' mun , who was caliph from 813 to 833 .
 person: Al-Ma ' mun
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 person: Al-Ma ' mun