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: Additionally , ecstasy users demonstrated impairments on tasks recruiting frontostriatal and hippocampal neural circuitry , in the domains of proactive interference memory , long - term memory , encoding , working memory and complex planning .
### Output Text:
Additionally , <span class="chemical">ecstasy</span> users demonstrated impairments on tasks recruiting frontostriatal and hippocampal neural circuitry , in the domains of proactive interference memory , long - term memory , encoding , working memory and complex planning . 