18566
It extends down the Tigris to Samarra and down the Euphrates to Hīt .
 Tigris, Samarra, Euphrates, Hīt
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Tigris, Samarra, Euphrates, Hīt