Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What is the highest diff with drawn of 6 and play larger than 18?

### Inputs:
table_name: table, columns: ['Team', 'Points', 'Played', 'Drawn', 'Lost', 'Against', 'Diff']

### Response:
SELECT MAX Diff FROM table WHERE Drawn = 6 AND Played > 18