A set of six cards with 1, 2, 3, 4, 5, and 6 written on them. Each person takes 2 cards from a group, no one is exactly the same. At least how many people have taken it can ensure that the numbers on the 2 cards taken by someone are mutually prime.
写有1、2、3、4、5、6的六张卡片为一组．每人从一组中取2张，没有完全相同的．至少多少人取过，才能保证有人取的2张卡片上的数互质．
<result>5</result>