验证卡布列克运算。任意一个四位数，只要它们各个位上的数字是不全相同的，就有这样的规律：

1)将组成该四位数的四个数字由大到小排列，形成由这四个数字构成的最大的四位数；

2)将组成该四位数的四个数字由小到大排列，形成由这四个数字构成的最小的四位数(如果四个数中含有0，则得到的数不足四位)；

3)求两个数的差，得到一个新的四位数(高位零保留)。

-Verify Kaprekar operation. Any one of the four-digit, as long as their individual bits on the same figures are incomplete, there is such a law: 1) the composition of the four four-digit numbers in descending order, formed by the composition of the four figures the largest four-digit　2) will be composed of the four-digit number from small to big four are arranged to form constituted by these four numbers, the smallest of the four-digit (if it contains the number of 4 0, then the number of less than 4)　3) Find the difference between two numbers, get a new four-digit (high to zero reservations).