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: Among the 15 patients with CIN , 6 had cyanotic congenital heart diseases , but the incidence did not differ significantly from that for the noncyanotic patients ( p = 0 . 243 ) .
### Output Text:
Among the 15 patients with CIN , 6 had cyanotic congenital heart diseases , but the incidence did not differ significantly from that for the noncyanotic patients ( p = 0 . 243 ) . 