class Student
{
 private:
         int id;
public:
         Student(int id)
         {
                  this->id = id;
          }
          friend void show(Student s, Professor p);
};


class Professor
{
private:
         string name;
public:
         Professor(string name)
         {
                  this->name = name;;
         }
         friend void show(Student s, Professor p);
};


void show(Student s, Professor p)
{
         cout << s.id << p.name;
}

int main()
{
         Student s1(123);
         Professor p1("t");
         void show(Student s1, Professor p1);
}


아무것도 안뜸ㅠㅠ