说明：  判断一个正数是否是质数。如果是质数，则输出“这个数是质数”；如果不是质数，则输出“这个数不是质数”。计算n的阶层以及从1的阶层到n的阶层之和。交换两个变量的值。计算一个一元二次方程的根。
(Judge if a positive number is a prime number.If it is a prime number, it outputs "This number is a prime number"; if it is not a prime number, it outputs "This number is not a prime number".Calculate the level of n and the sum of the level from 1 to n. Swap the values of two variables. Calculate the root of a unary quadratic equation.)