What does the story told by superintendent Huang in Infernal Affairs 1 mean?

"Once upon a time, there were two fools waiting for a kidney transplant in the hospital, but they only had one kidney. So they decided to play a game. Put the playing cards in the opponent's pocket, and whoever can guess what cards the opponent puts for himself will win. "

"Supplement: Whoever guesses wrong will die."

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The meaning of this story is that police officer Huang compares himself and the way to two idiots in the hospital, and those two cards are "and". Officer Huang broke the story of the way and made sure that the other party arranged undercover for him, but he didn't know which one at that time and told the story. Brother Chen and sir Huang are both smart people, and everyone knows what it means when telling stories.