1493
Numerous lines of evidence suggest that heterocyclic compounds used as analgesic , anti - inflammatory and anti - migraine agents can be potent regulators of the nitroxidative stress and targeting free nitrogen and oxygen radicals is a very promising strategy for future pain management .
 Chemical: nitrogen; Chemical: oxygen
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: nitrogen, oxygen 
Answer:
 Chemical: nitrogen; Chemical: oxygen