这个程序是用来判断一个数是否为素数的，用户由键盘输入一个正整数，即可判断该数是否为素数，还可以连续输入，输入-1来结束输入。-This procedure is used to determine whether a number of prime numbers, the user keyboard input from a positive integer, you can determine whether the number of prime numbers, but also for