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: Compliance to niacin extended - release / lovastatin was 77 % , with 3 , 245 patients completing the study .
### Output Text:
Compliance to <span class="chemical">niacin extended - release / lovastatin</span> was 77 % , with 3 , 245 patients completing the study . 