In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: AIM : To examine whether paracetamol - induced acute liver failure increases long - term mortality .
### Output Text:
AIM : To examine whether <span class="chemical">paracetamol</span> - induced acute liver failure increases long - term mortality . 