Complete a sentence that means the same as the following sentence, but is more concise:
He had no idea what I was talking about.
He was clueless.
Complete the following task based on the instruction and optional input provided.### Instruction:
Complete a sentence that means the same as the following sentence, but is more concise:

### Input:
He had no idea what I was talking about.

### Output:
He was clueless.