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: These data indicate that ( 1 ) the apparent incidence of stroke related to cocaine use is increasing ; ( 2 ) cocaine - associated stroke occurs primarily in young adults ; ( 3 ) stroke may follow any route of cocaine administration ; ( 4 ) stroke after cocaine use is frequently associated with intracranial aneurysms and arteriovenous malformations ; and ( 5 ) in cocaine - associated stroke , the frequency of intracranial hemorrhage exceeds that of cerebral infarction .
### Output Text:
These data indicate that ( 1 ) the apparent incidence of stroke related to <span class="chemical">cocaine</span> use is increasing ; ( 2 ) <span class="chemical">cocaine</span> - associated stroke occurs primarily in young adults ; ( 3 ) stroke may follow any route of <span class="chemical">cocaine</span> administration ; ( 4 ) stroke after <span class="chemical">cocaine</span> use is frequently associated with intracranial aneurysms and arteriovenous malformations ; and ( 5 ) in <span class="chemical">cocaine</span> - associated stroke , the frequency of intracranial hemorrhage exceeds that of cerebral infarction . 