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: BACKGROUND : Acetaminophen - induced hepatotoxicity is the most common cause of acute liver failure ( ALF ) in the UK .
### Output Text:
BACKGROUND : <span class="chemical">Acetaminophen</span> - induced hepatotoxicity is the most common cause of acute liver failure ( ALF ) in the UK . 