多维数组元素的访问 越界

int a[3][3]={1,2,3,4,5,6,7,8,9};
int i=1,j=1;
int (*p)[3];
p=a;
cout<<"*(*(a+i)+j)= "<<*(*(a+i)+j)<<endl;
cout<<"*(a[i]+j)= "<<*(a[i]+j)<<endl;
cout<<"*(a+i)[j]= "<<*(a+i)[j]<<endl;
cout<<"*(a+3*i+j)= "<<*(a+3*i+j)<<endl;
cout<<"*(*(p+i)+j)= "<<*(*(p+i)+j)<<endl;
cout<<"*(p[i]+j)= "<<*(p[i]+j)<<endl;
cout<<"*(p+i)[j]= "<<*(p+i)[j]<<endl;
cout<<"*(p+3*i+j)= "<<*(p+3*i+j)<<endl;
cout<<"p[i][j]= "<<p[i][j]<<endl;

值为7的地方越界了吧？ 为什么是7啊 怎么。。