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: The mean duration of therapy with cabergoline was 523 . 5 + / - 129 . 7 days , and the mean duration of therapy with risperidone was 788 . 5 + / - 162 . 5 days .
### Output Text:
The mean duration of therapy with <span class="chemical">cabergoline</span> was 523 . 5 + / - 129 . 7 days , and the mean duration of therapy with <span class="chemical">risperidone</span> was 788 . 5 + / - 162 . 5 days . 