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: We suggest that ecstasy - associated dysfunction in fronto - temporal circuitry may underlie overnight consolidation memory impairments in regular ecstasy users .
### Output Text:
We suggest that <span class="chemical">ecstasy</span> - associated dysfunction in fronto - temporal circuitry may underlie overnight consolidation memory impairments in regular <span class="chemical">ecstasy</span> users . 