Ошибка ввода данных

#include <iostream>
using namespace std;
 
struct Student
{
    char name[50];
    int group;
 
    union Exam
    {
        unsigned subject : 1;
    }mark;
 
}student;
 
void Sort(int size, int myArray[])
{
    int tmp;
    for (int i = 0; i < size; i++)
    {
        for (int j = size - 1; i > 0; i++)
        {
            tmp = myArray[i];
            myArray[j] = myArray[j - 1];
            myArray[j - 1] = tmp;
        }
    }
 
    for (int s = 0; s <size; s++)
    {
        cout << myArray[s] << endl;
    }
}
 
void main()
{
    Student myArray[30];
 
    int i = 0;
    int choose;
 
    do
    {
        cout << "Please enter the name of the student: " << endl;
        cin.getline(student.name, sizeof(student.name));
 
        cout << "Please enter the group: " << endl;
        cin >> student.group;
 
        int markOftheStudent;
        cout << "Pelase enter thee mark in order to put offster/fail" << endl;
        cin >> markOftheStudent;
 
        if (markOftheStudent > 5 || markOftheStudent < 1)
        {
            cout << "Error: 5-point system only" << endl;
        }
        else if (markOftheStudent == 5 || markOftheStudent == 4 || markOftheStudent == 3)
        {
            cout << "OFSTER" << endl;
        }
        else
        {
            cout << "FAIL EXAM" << endl;
        }
 
        while (markOftheStudent < 0 || markOftheStudent>5);
        student.mark.subject = markOftheStudent;
 
        cout << "\nKeep filling the teacher's list ? 0-no,1-yes:" << endl;
        cin >> choose;
 
    } while (choose!=0);
}

cin >> choose;

cin.ignore();