Black to move
A position from the 2013 U.S. Championship in Saint Louis.
Grandmaster Yury Shulman is playing White against Jorge Sammour-Hasbun.
White is in big trouble, but Black went wrong with 19...0-0.
Shulman continued with 20.Ke2! and even won the game later.
Black has a much stronger move than 19...0-0. Can you find it?