39840
In August 2015 , the main characters of both games in the " Left 4 Dead " series were also added exclusively to the PC version 's playable character roster .
 Left 4 Dead
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Left 4 Dead