求各路大神看看程序

#include<iostream>
#include<ctime>
using namespace std;
int main()
{
    int numberOne, numberTwo, sum;
    char loop='Y';

    srand(time(0));                                          //根据系统时间设置随机数种子
    while('N'!=loop);                                        //loop等于n时停止循环
    {
        numberOne=rand()%100;
        numberTwo=rand()%100;
        cout<<numberOne<<"+"<<numberTwo<<"=?"<<endl;
        cin>>sum;
        if(sum==numberOne+numberTwo){
            cout<<"Congratulations!"<<endl;
        }
        else{
            cout<<"Sorry,correct answer is:"<<numberOne+numberTwo<<endl;
        }
        cout<<"try again (Y/N)?";
        cin>>loop;
        loop=toupper(loop);                                   //将loop变量的值变成大写字母
    }
    return 0;
}
我这个程序是抄的书上的，在编译的时候显示无错误，但是无法运行，又大神可以看看吗？（我用的是VC#6版本的编译器）