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The paper said Beijing helps to cap its population at 1 . 6 billion by the year 2050 .
 Beijing, its, its population, 1 . 6 billion
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: geographical social political, organization, person, location, facility, vehicle, weapon 
Text: {0} 
Answer:
 Beijing, its, its population, 1 . 6 billion