大佬们，求助！

大佬们，这个怎么解决
#include<iostream>
#include<string>
using namespace std;
class Undergraduate
{
public:
Undergraduate()
{
}
void GetUndergraduate(int id, string name, string specialty)
{
m_id = id;
m_name = name;
m_specialty = specialty;
}
void Showinfo()
{
cout << "姓名：" << m_name << " 专业：" << m_specialty << " 学号：" << m_id << endl;
}
private:
int m_id;
string m_name;
string m_specialty;
};
class Graduate :public Undergraduate
{
public:
Graduate(string teacher, int PapersNumber)
{
m_teacher = teacher;
m_PapersNumber = PapersNumber;
}
void Showinfo()
{
Undergraduate::Showinfo();
cout << "导师:" << m_teacher << " 发表论文数:" << m_PapersNumber << endl;
}
private:
string m_teacher;
int m_PapersNumber;
};
int main()
{
Graduate gra("罗翔", 129);
gra.GetUndergraduate(101, "张三", "电子信息类");
gra.Showinfo();
Graduate gra2("宋浩", 87);
gra2.GetUndergraduate(102, "李四", "电子信息类");
gra2.Showinfo();
system("pause");
return 0;
}