下列程序的输出结果是非曲直 【15】 。
#include＜iostream, h＞
class base int x, y;
public:
base(int i, int j)x=i; y=j;
virtual int add()return x+ y;
;
class three: public base int z;
public:
three(int i, int j, int k) :base(i, j)z=k;
int add() return (base:: add()+z);
;
void main() three * q=new three(lO,20,30);
cout＜＜q-＞add()＜＜end1;