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

### Instruction:
What is the margin when periyakulam is the constituency?

### Inputs:
table_name: table, columns: ['Constituency', 'Winner', 'Party', 'Margin', 'Runner-up a', 'Party a']

### Response:
SELECT Margin FROM table WHERE Constituency = Periyakulam