有如下程序: #include<iostream> using namespace std; class Part{ public: Part(int x=0):val(x) {cout<<val;} ~Part(){cout<<val;} private: int val; }; class Whole{ public: Whole(int x ,int y, int z=0):p2(x),p1(y),val(z){cout<<val;} ~Whole(){cout<<val;} private: Part p1,p2; int val; }; int main() Whole obj(1,2,3); return 0; } 程序的输出结果是( )。