3rd Prices Information Cup, League D, Rui Naiwei - Choi Wonyong

This position from game between Rui Naiwei, 9р, and Choi Wonyong, 5p, from 3rd Prices Information Cup. The next sequence is classic tesuji from gandicap game.
After that moves black successfully outgoing in center.
After 17 move, black can connect two stones, but in real game Rui Naiwei select to attack white stones on left side. The main idea was - create territory on lower side and in centre.

Rui Naiwei(9p) - Choi Wonyong(5p) - W+4.5