想建立一单链表   
提示的信息为:
             fatal error C1903: unable to recover from previous error(s); stopping compilation
#include<iostream>
#include<string>
using namespace std;
struct stu
{
    int num;
    stu *next;
};
void main()
{
    stu H=Null;
    stu *s;
    int x;
    cin>>x;
    while(x!=NULL)
    {
        s=malloc(sizeof(Lnode));
        s->num=x;
        s->next=H;
        H=s;
        cin>>x;
    }
    while(H!=NULL)
    {
        cout<<H->num" ";
        H=H->next;
    }
    cout<<endl;
}
找半天没找到错在哪

stu H=Null;程序中是stu *H=NULL;