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 present the case of a 31 - year - old man with bilateral ischemia of the globus pallidus after excessive alcohol and intranasal cocaine use .
### Output Text:
We present the case of a 31 - year - old man with bilateral ischemia of the globus pallidus after excessive <span class="chemical">alcohol</span> and intranasal <span class="chemical">cocaine</span> use . 