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: The number of nocturia episodes decreased from 5 . 4 + / - 4 . 2 to 1 . 1 + / - 1 . 0 times per night .
### Output Text:
The number of nocturia episodes decreased from 5 . 4 + / - 4 . 2 to 1 . 1 + / - 1 . 0 times per night . 