Determine the oxidation number of following underline elements:
`HulCN`

Explanation

To determine the oxidation number of carbon in the compound HCN (hydrogen cyanide), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the elements and their known oxidation states**:
- In HCN, we have three elements: Hydrogen (H), Carbon (C), and Nitrogen (N).
- The oxidation state of hydrogen (H) is typically +1.
- The oxidation state of nitrogen (N) in cyanide (CN) is -3.
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