A look through

Before you perform the trick, prepare the deck in a special way: collect all the red cards on the top of the deck, and all the black cards in the bottom of the deck. After that, take the deck face down and let any of the viewers draw any card from the top of the deck (this will be a red card), then let the other viewer draw any card from the bottom of the deck (this will be a black card). Next, ask the first spectator to put the card in the lower part of the deck, and place the second spectator in the top of the deck. Then collect the deck, quickly flipping through it, and noticing the only black card among the red cards and the only red card among the black cards. When you see these cards, shuffle the deck and give it to the audience so that they check it. After the deck is returned to you, you turn the cards and get those that the audience has chosen.