import java.util.Scanner;

public class StudentManagement {
    Student[] students = new Student[100];
    int n = 0;


    public static boolean sameGroup(Student s1, Student s2) {
        if (s1.getGroup().equals(s2.getGroup()))
            return true;
        else
            return false;
    }

    public void addStudent(Student newStudent) {

        students[n] = newStudent;
        n++;
        //System.out.println("Huy");
    }

    public String studentsByGroup() {
        String[] groups = new String[100];
        Integer[] flags = new Integer[100];
        String s = "";
        int count = 0;
        for (int i = 0; i < n; i++) {
            if (flags[i] == null) {
                groups[count] = students[i].getGroup();
                count++;
                flags[i] = i + 1;
                for (int j = i + 1; j < n; j++)
                    if ((flags[j]==null) && students[i].getGroup().equals(students[j].getGroup()))
                        flags[j] = flags[i];
            }
        }

        for (int i = 0; i < count; i++) {
            if (i==0) s += groups[i]; else s+= "\n"+groups[i];
            for (int j = 0; j < n; j++)
                if (students[j].getGroup().equals(groups[i]))
                    s = s + "\n" + students[j].getInfo();

        }
        return s;
    }

    public void removeStudent(String id) {
        for (int i = 0; i < n; i++)
            if (students[i].getId().equals(id)) {
                for (int j = i; j < n - 1; j++)
                    students[j] = students[j + 1];
                break;
            }
        students[n - 1] = null;
        n--;

    }


}