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: Haloperidol enhanced the rigidity in the A group .
### Output Text:
<span class="chemical">Haloperidol</span> enhanced the rigidity in the A group . 