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: S - 1 may be administered safely to patients with 5 - FU - induced cardiotoxicity .
### Output Text:
S - 1 may be administered safely to patients with <span class="chemical">5 - FU</span> - induced cardiotoxicity . 