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

### Instruction:
What is the lowest laps that has a manufacturer of yamaha, and a time/retired of +1:08.312, and a grid less than 20?

### Inputs:
table_name: table, columns: ['Rider', 'Manufacturer', 'Laps', 'Time/Retired', 'Grid']

### Response:
SELECT MIN Laps FROM table WHERE Manufacturer = yamaha AND Time/Retired = +1:08.312 AND Grid < 20