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

### Instruction:
What is the horizontal bar score with a pommel horse of n/a, and the position is less than 27, and the parallel bars score is 15.800?

### Inputs:
table_name: table, columns: ['Position', 'Gymnast', 'Floor', 'Pommel Horse', 'Rings', 'Vault', 'Parallel Bars', 'Horizontal Bar', 'Total']

### Response:
SELECT Horizontal Bar FROM table WHERE Pommel Horse = n/a AND Position < 27 AND Parallel Bars = 15.800