有以下程序 #include ＜iostream＞ using namespace std; class Base { int a; public: Base(int x){ a=x; } void show(){ cout＜＜a; } class Derived : public Base { int b; public: Derived(int i) :Base(i+1),b(i){} void show() { cout＜＜b; }; int main () { Base b(5),*pb; Derived d(1); pb=&d; pb-＞show (); return 0; } 运行后的打印结果是______。