Poker has a magical power. When we see that the magician has a dazzling shuffle, shuffle and flop, the desired card appears in his hand. In fact, it is done by using the knowledge of "median" in mathematics. First, take a deck of playing cards and ask a classmate to randomly draw 15 cards from this deck (note: random drawing must be emphasized to increase the magic effect. Then do the following: (1) unfold the cards for others and ask a classmate to choose a card from this 15 card in his mind. (2) Put the cards together first, and then divide the cards into three columns from top to bottom in the order of 1 to 15, that is, after the first student confirms, each column is placed in the middle column. ] The second time the cards were divided, they were in the second, third and fourth rows, and the second student confirmed them and put them in the middle column. At this time, its interval range in the new sequence 2 is [7,9], and [7,9] is in the third row when the cards are divided for the third time. After the third student confirms, five cards are put. (3) Hold up a list of cards and ask the students to identify the cards he selected.