user: Question: What is the lowest block for director Graeme Harper?
Columns: ['Block', 'Director', 'Writers', 'Producer', 'Code']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'Euros Lyn', 'Russell T Davies', 'Phil Collinson', '3X']
SQL:

assistant: SELECT MIN("Block") FROM "Table" WHERE "Director" = 'Graeme Harper';