有如下程序：
#include＜iostream＞
using namespace std;
class ONE
public:
virtual void f() cout ＜＜ "1";
;
class TWO: 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是______
