Your turn to fire the first shot. Black has: a row-7 three with white's (9,7) capping its right end — a rush four waiting at (8,7), whose only five point (4,7) white must hold; a column-7 three capped at the top by (7,10) — the second four; and the row-6 pair already lying in wait to become the open four that ends the game. Start the chain at the correct point: the order is not optional, because each four must leave the next one intact.
Finish this step to move on.