7716
For instance , one of the standard proofs of Lagrange 's four-square theorem , that every positive integer can be represented as a sum of four squares , is based on quaternion GCDs in this way .
 Lagrange
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Lagrange