using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        while (true)

        {

            Dictionary<string, double> studentGrades = new Dictionary<string, double>();

            while (true)

            {

                Console.Write("Enter a student's name (or type 'done' to finish): ");

                string studentName = Console.ReadLine();

                if (studentName.ToLower() == "done")

                {

                    break;

                }

                else

                {

                    Console.Write($"Enter {studentName}'s grade (0-100): ");

                    string studentGrade = Console.ReadLine();

                    if (int.TryParse(studentGrade, out int grade))

                    {

                        if (grade >= 0 && grade <= 100)

                        {

                            studentGrades[studentName] = grade;

                        }

                        else

                        {

                            Console.WriteLine("Invalid input! Please enter a number between 0-100.");

                        }

                    }

                    else

                    {

                        Console.WriteLine("Invalid input! Please enter an integer.");

                    }

                }

            }

​

            if (studentGrades.Count > 0)

            {

                int studentCount = studentGrades.Count;

                Console.WriteLine($"Total students: {studentCount}");

​

                double totalGrade = studentGrades.Values.Sum();

                double averageGrade = totalGrade / studentCount;

                Console.WriteLine($"Class average: {averageGrade:F2}");

                var highestGradeEntry = studentGrades.FirstOrDefault(entry => entry.Value == studentGrades.Values.Max());

                Console.WriteLine($"Highest grade: {highestGradeEntry.Key} with {highestGradeEntry.Value:F2}");

​

                var lowestGradeEntry = studentGrades.FirstOrDefault(entry => entry.Value == studentGrades.Values.Min());

                Console.WriteLine($"Lowest grade: {lowestGradeEntry.Key} with {lowestGradeEntry.Value:F2}");

                Console.WriteLine("What would you like to do?");

                Console.WriteLine("- Type 'search' to search for a student's grade");

                Console.WriteLine("- Type 'update' to update a student's grade");

                Console.WriteLine("- Type 'reset' to reset all data and start over");

                string actionChoice = Console.ReadLine();

                if (actionChoice.ToLower() == "search")

                {

                    Console.WriteLine("Enter the student's name: ");

                    string searchStudent = Console.ReadLine();

                    var searchEntry = studentGrades.FirstOrDefault(entry => entry.Key == searchStudent);

                    Console.WriteLine($"{searchStudent}'s grade is: {searchEntry.Value:F2}.");

                }

                else

                {

                    Console.WriteLine("No student entries found. Data will not be shown.");

                }

            }

                Console.WriteLine("Would you like to reset and start over? (yes/no)");

                string resetChoice = Console.ReadLine();

                if (resetChoice != "yes")

                {

                    Console.WriteLine("Thank you!");

                    break;

                }

            }

        }

}