Generate a unique username that follows the company's standard guidelines.
User's name: Mason Miller
Your unique username based on our company standard guidelines could be MasMil_23.
Complete the following task based on the instruction and optional input provided.### Instruction:
Generate a unique username that follows the company's standard guidelines.

### Input:
User's name: Mason Miller

### Output:
Your unique username based on our company standard guidelines could be MasMil_23.