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: There were 3379 patients randomly assigned to enalapril with a median follow - up of 974 days and 3379 patients randomly assigned to placebo with a mean follow - up of 967 days .
### Output Text:
There were 3379 patients randomly assigned to <span class="chemical">enalapril</span> with a median follow - up of 974 days and 3379 patients randomly assigned to placebo with a mean follow - up of 967 days . 