有下列程序：
#include＜iostream＞
using namespace std;
class ONE
{
public:
virtual void f(){COUt＜＜"1";}
};
c1assTWO:public ONE
{
public:
TWO(){cout＜＜"2";}
};
class THREE:public TWO
{
public:
virtual void f(){TWO∷f();cout＜＜"3";}
};
int main()
{
ONE aa,*p;
TWO bb;
THREE cc;
p=&cc;
p-＞f();
return 0;
}
执行上面程序的输出结果是______。