/ is 3, which is a natural number between 2 and 4, and is also an odd number and a positive integer. is the second prime number starting from 0, and 3 is the third non-zero natural number and the first Mersenne prime, so it can imply making a friend. Friends should be frank and treat each other sincerely. The number 3 means that you have no two hearts and one mind for your friends. Therefore, 3 is the most reasonable explanation.