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: CASE REPORT : We describe 2 patients who were regular consumers of alcohol and who developed liver failure within 3 - 5 days after hospitalization and stopping alcohol consumption while being treated with 4 g paracetamol / day .
### Output Text:
CASE REPORT : We describe 2 patients who were regular consumers of <span class="chemical">alcohol</span> and who developed liver failure within 3 - 5 days after hospitalization and stopping <span class="chemical">alcohol</span> consumption while being treated with 4 g <span class="chemical">paracetamol</span> / day . 