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: We presented a patient admitted to our out - patient clinic with diffuse skeletal pain after three consecutive administration of alendronate .
### Output Text:
We presented a patient admitted to our out - patient clinic with diffuse skeletal pain after three consecutive administration of <span class="chemical">alendronate</span> . 