static void Main(string[] args)
{
List <Mark> marks = new List <Mark> {
new Mark(new DateTime(2021, 3, 12), 12), new Mark(new DateTime(2021, 4, 2), 11), new Mark(new DateTime(2021, 5, 23), 10)
};
Student student = new Student(marks, "Eugene");
Console.WriteLine(student.ToString());
Console.WriteLine($"Average mark: {student.getAverageMark()}");
student.CancelMark(1);
Console.WriteLine("Canceled mark:");
Console.WriteLine(student.ToString());
Console.WriteLine($"Average mark: {student.getAverageMark()}");
}
