19683
The 1 , 3 , 4 - thiadiazole nucleus is one of the most important and well - known heterocyclic nuclei , which is a common and integral feature of a variety of natural products and medicinal agents .
 Chemical: 1 , 3 , 4 - thiadiazole
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: 1 , 3 , 4 - thiadiazole