一个计算机类，想用一下纯虚函数写一下多态，但不管输入什么结果都是0呢？

#include<iostream>
using namespace std;
class Calculator{
	public:
		virtual int GetRusult(){
			return 0;
		}
	int m_num1;
	int m_num2;
};
class addCalculator:public Calculator{
	public:
		int GetResult(){
			return m_num1+m_num2;
		}
};
class subCalculator:public Calculator{
	public:
		int GetResult(){
			return m_num1 - m_num2;
		}
};
class mulCalculator:public Calculator{
	public:
		int GetResult(){
			return m_num1*m_num2;
		}
};
class divCalculator:public Calculator{
	public:
		int GetResult(){
			return m_num1/m_num2;
		}
};
void test01(){
	Calculator *p= new mulCalculator;
	p->m_num1=100;
	p->m_num2=300;
	cout<<p->GetRusult()<<endl;
	delete p;
}
int main(){
	test01();
}