1555
The word " existential " can even be dropped from the previous characterization , since " P " = " NP " if and only if " P " = " PH " ( as the former would establish that " NP " = " co-NP " , which in turn implies that " NP " = " PH " ) .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 None