#include <stdio.h>

#include <math.h>

#include <windows.h>

int pan(int i);                                  //声明一个函数;

int main(void)

{

       int i,k;

       while(1)                                   //可以多次输入不同的数进行判断;

       {

       scanf("%d",&i);

       if(i<1)                                      //输入i<1时退出程序，此处需要和window.h的头文件一起使用;

       {

              printf("输入错误！！！");

              exit(1);

       }

       k=pan(i);                                         //进入函数;

       if(k==0)

              printf("该数为素数！\n");

       else

              printf("该数不是素数！\n");

       }    

       return 0;             

}

int pan(int i)                                   //判断函数;

{

       int a=0,j,t=i;       

       for(j=2;j<=sqrt(i);j++)                          //开方判断,减少不必要的运算;

       {

              if(t%j==0)                                             //如果对该数求余为0，说明该数为合数;

              {

                     a=1;             

                     break;

              }

       }

       return a;

}