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 third patient had acute amphetamine - induced chorea after prolonged oral contraception .
### Output Text:
The third patient had acute <span class="chemical">amphetamine</span> - induced chorea after prolonged <span class="chemical">oral contraception</span> . 