多级派生情况下派生类的构造函数

#include<iostream>
#include<string>
using namespace std;
class Student
{
public:
 Student(int n,string nam)
 {
  num=n;
  name=nam;
 }
 void display()
 {
  cout<<"num:"<<num<<endl;
  cout<<"name:"<<name<<endl;
 }
 ~Student(){}
protected:
 int num;
 string name;
};

class Student1:public Student
{
public:
 Student1(int n,string nam,int a):
   Student(n,nam)
   {
        age=a;
   }
 void show()
 {
  display();
  cout<<"age:"<<age<<endl;
 }
 ~Student1(){}
private:
 int age;
};

class Student2:public Student1
{
public:
 Student2(int n,string nam,int a,double s):
   Student1(n,nam,a)
   {
    score=s;

   }
 void show_all()
 {
  show();
  cout<<"score:"<<score<<endl;
 }
 ~Student2(){}
private:
 double score;
};

int main()
{
 Student2 stud2(2008482271,"帅哥",24,100);
 stud2.show_all();
 return 0;
}