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: RESULTS : All groups exhibited similar training latencies ( 17 . 0 + / - 4 . 6 s ) .
### Output Text:
RESULTS : All groups exhibited similar training latencies ( 17 . 0 + / - 4 . 6 s ) . 