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: Five of the 13 patients ( 38 % ) with pain and seven of the 41 patients ( 17 % ) without pain admitted to a high alcohol intake , which might be a contributing factor .
### Output Text:
Five of the 13 patients ( 38 % ) with pain and seven of the 41 patients ( 17 % ) without pain admitted to a high <span class="chemical">alcohol</span> intake , which might be a contributing factor . 