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

### Instruction:
What series number was directed by milan cheylov and written by will dixon?

### Inputs:
table_name: table, columns: ['Series #', 'Title', 'Directed by', 'Written by', 'Original air date']

### Response:
SELECT AVG Series # FROM table WHERE Directed by = milan cheylov AND Written by = will dixon