hajoucha: I find it highly frustrating that collection rated with average difficulty of 21k contains problems rated as 4d. Do you really think 4d needs to practice 21k problems? Or 21k needs to practice 4d problems?
d4rkm4tter: No it is not. If opponent plays the correct move, there is no solution. Move 4 opponent has a correct and an incorrect move, so he will always play the move that is red for the player.
Ivan Detkov: I see. This task is incorrect in such case.
I see. This task is incorrect in such case.