填空题

下列程序的输出结果为2,请将程序补充完整。
#include<iostream>
using namespace std;
class Base
public:
______void fun()cout<<1;

class Derived:public Base
public:
void fun()cout<<2;

int main()
Base*p=new Derived;
p->fur();
delete p;
return 0;

【参考答案】

virtual