#include<iostream>
#include<cmath>
using namespace std;
void judge(int number)
{  int i,flag=1;
   for(i=2;i<=sqrt(number);i++)
   { if(number%i==0) {flag=0;
                      break;
   
                     }
    }
   if(flag==0) cout<<number<<"不是素數"<<endl;
   else cout<<number<<"是素數"<<endl;
  
     
     }
int main()
{  int number;
   char require='y';
  while((require=='y'))||(require=='Y'))
   {          

    cout<<"please input a number:  ";
    cin>>number;
      judge(number);
    cout<<"請問您想繼續嗎？y/n？";
    cin>>require;
    }
    
  
    system("pause");
    return 0;
  }