有如下程序: #include <iostream> using namespaee std; class ONE public: virtual void f( )cout<<"1"; ; class TWO:public ONE public: TWO( )1 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; 程序的输出结果是______。