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: INTRODUCTION AND OBJECTIVE : Contrast - induced nephropathy ( CIN ) significantly increases the morbidity and mortality of patients .
### Output Text:
INTRODUCTION AND OBJECTIVE : <span class="chemical">Contrast</span> - induced nephropathy ( CIN ) significantly increases the morbidity and mortality of patients . 