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: Exercise - induced ST depression was observed in 84 % of the non - MI group , 43 % of the ANT - MI group , 38 % of the INF - MI group and 61 % of the total .
### Output Text:
Exercise - induced ST depression was observed in 84 % of the non - MI group , 43 % of the ANT - MI group , 38 % of the INF - MI group and 61 % of the total . 