Although the first diagram was long considered the solution, Go Seigen came up with this , the tesuji known as the ugly sagari. So really there is nothing black can do. The problem is now often given as a problem for white, how to respond to
Anon: What happens if B plays at ?
unkx80: I guess this. Note, has no time to play the throw-in at , as can capture by snapback at a.