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: While the use of MDMA in quantities that may be considered " moderate " is not associated with impaired memory functioning , heavy use of MDMA use may lead to long lasting memory impairments .
### Output Text:
While the use of <span class="chemical">MDMA</span> in quantities that may be considered " moderate " is not associated with impaired memory functioning , heavy use of <span class="chemical">MDMA</span> use may lead to long lasting memory impairments . 