16718
He was the eldest son of Robert I of Flanders and Gertrude of Saxony .
 organization: Robert I of Flanders; person: Gertrude of Saxony
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities: Robert I of Flanders, Gertrude of Saxony 
Answer:
 organization: Robert I of Flanders; person: Gertrude of Saxony