using System;

using System.Collections.Generic;

​

public class ThingDo

{

    private string FindGrade()

    {

        var s = new Stuff();

        if (s.Grade == 100) return "AAAAAAAAAAAAAAAAAAAAAAAAAAAAA";

        if (s.Grade < 60)

        {

            return "F";

        }

        foreach (var dItem in s.grades)

        {

            if (s.Grade >= dItem.Key)

                return dItem.Value;

        }

        return "UNGRADED";

    }

​

    public string GetGrade()

    {

        return FindGrade();

    }

    public void DisplayGrade()

    {

        Console.WriteLine(GetGrade());

    }

}

​

public class Stuff

{

    private int grade = 100;

    public int Grade

    {

        get => grade;

        private set => grade = value;

    }

    public readonly Dictionary<int, string> grades = new Dictionary<int,string>

    {

        { 90, "A" },

        { 80, "B" },

        { 70, "C" },

        { 60, "D" }

    };

}

​

public class Program

{

    public static void Main()

    {

        ThingDo td = new();

        td.DisplayGrade();

    }

}