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: Early CY toxicity caused a typical haemorrhagic cystitis in both strains that was completely repaired in about 7 - 10 days .
### Output Text:
Early <span class="chemical">CY</span> toxicity caused a typical haemorrhagic cystitis in both strains that was completely repaired in about 7 - 10 days . 