运算符·重载

#include <iostream>
#include <string>
using namespace std;

class Student{
    int grade;
    string name;
     
public:
    static int num;
Student(){
    grade=0;
    name="123";
}
Student(string b,int a):grade(a),name(b){}        
~Student(){}
friend istream &operator>>(istream  &input,Student &st)//必须是friend 
      { 
         input >> st.name>> st.grade ;num++;
         return input;          
      }    
friend ostream &operator<<(ostream  &output,Student &st)
      { 
         output<<st.num<<'.'<<' '<<st.name<<' '<<(st.grade>=60? "PASS":"FAIL"); 
         return output;         
      }    
      
};
 
int Student::num=0;

int main(){
    int i, repeat;
    Student st;
    cin>>repeat;
    for(i=0;i<repeat;i++){
        cin>>st;
        cout<<st<<endl;
    }
    return 0;
}