70. cannon and screen together, by the cannon

Helpmates in xiangqi

4 moves

Black moves first and both sides cooperate: Black, Red, Black, Red, and Red's second move mates. Black has 46 legal first moves and exactly one of them works. 11 pieces, Black 27.5 to Red 6.5 in material, mate by the cannon. Themes: cannon and screen together, Black blocks its ow…