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

### Instruction:
How many directors of episode 55?

### Inputs:
table_name: table, columns: ['Series no.', 'No. in season', 'Title', 'Written by', 'Directed by', 'Original air date']

### Response:
SELECT COUNT Directed by FROM table WHERE Series no. = 55