Задача про структуры

#include <iostream>
#include <string>
using namespace std;
 
struct student {
    string name;
    string second_name;
    int age;
    int clas;
    int num_marks;
    int marks[30];
};
void add_mark(student &s)
{
    double average = 0;
    for (int i = 0; i < s.num_marks; i++)
        average += s.marks[i];
    average /= s.num_marks;
    while (average < 4.5)
    {
        s.marks[s.num_marks] = 5;
        s.num_marks += 1;
        for (int i = 0; i < s.num_marks; i++)
            average += s.marks[i];
        average /= s.num_marks;
    }
}
 
int main()
{
    student a;
    cin >> a.name >> a.second_name >> a.age >> a.clas >> a.num_marks;
    for (int i = 0; i < a.num_marks; i++)
        cin >> a.marks[i];
    student b;
    cin >> b.name >> b.second_name >> b.age >> b.clas >> b.num_marks;
    for (int i = 0; i < b.num_marks; i++)
        cin >> b.marks[i];
    student c;
    cin >> c.name >> c.second_name >> c.age >> c.clas >> c.num_marks;
    for (int i = 0; i < c.num_marks; i++)
        cin >> c.marks[i];
    student d;
    cin >> d.name >> d.second_name >> d.age >> d.clas >> d.num_marks;
    for (int i = 0; i < d.num_marks; i++)
        cin >> d.marks[i];
    student e;
    cin >> e.name >> e.second_name >> e.age >> e.clas >> e.num_marks;
    for (int i = 0; i < e.num_marks; i++) 
        cin >> e.marks[i];
    add_mark(a);
    add_mark(b);
    add_mark(c);
    add_mark(d);
    add_mark(e);
    cout << a.name << " " << a.second_name << " " << a.age << " " << a.clas << " " << a.num_marks << endl;
    for (int i = 0; i < a.num_marks; i++)
        cout << a.marks[i] << " ";
    cout << endl;
    cout << b.name << " " << b.second_name << " " << b.age << " " << b.clas << " " << b.num_marks << endl;
    for (int i = 0; i < b.num_marks; i++)
        cout << b.marks[i] << " ";
    cout << endl;
    cout << c.name << " " << c.second_name << " " << c.age << " " << c.clas << " " << c.num_marks << endl;
    for (int i = 0; i < c.num_marks; i++)
        cout << c.marks[i] << " ";
    cout << endl;
    cout << d.name << " " << d.second_name << " " << d.age << " " << d.clas << " " << d.num_marks << endl;
    for (int i = 0; i < d.num_marks; i++)
        cout << d.marks[i] << " ";
    cout << endl;
    cout << e.name << " " << e.second_name << " " << e.age << " " << e.clas << " " << e.num_marks << endl;
    for (int i = 0; i < e.num_marks; i++)
        cout << e.marks[i] << " ";
    system("pause");
    return 0;
}