82418
As of 1998 , the then-current degree of southward expansion of the Sahara was not well known , due to a lack of recent , measurable expansion of the desert into the Sahel at the time .
 location: Sahara; location: Sahel
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: Sahara, Sahel 
Answer:
 location: Sahara; location: Sahel