public static void Main()
Console.WriteLine("Plesase enter your grade. (0~22) To exit this program, enter -1.");
int grade = int.Parse(Console.ReadLine());
Console.WriteLine("Your grade is H : Not specified. Plesase enter your grade. (0~22) To exit this program, enter -1.");
grade = int.Parse(Console.ReadLine());
Console.WriteLine("Your grade is G : Very Poor. Plesase enter your grade. (0~22) To exit this program, enter -1.");
grade = int.Parse(Console.ReadLine());
Console.WriteLine("Your grade is F : Poor. Plesase enter your grade. (0~22) To exit this program, enter -1.");
grade = int.Parse(Console.ReadLine());
Console.WriteLine("Your grade is E : Weak. Plesase enter your grade. (0~22) To exit this program, enter -1.");
grade = int.Parse(Console.ReadLine());
Console.WriteLine("Your grade is D : Satisfactory. Plesase enter your grade. (0~22) To exit this program, enter -1.");
grade = int.Parse(Console.ReadLine());
Console.WriteLine("Your grade is C : Good. Plesase enter your grade. (0~22) To exit this program, enter -1.");
grade = int.Parse(Console.ReadLine());
Console.WriteLine("Your grade is B : Very Good. Plesase enter your grade. (0~22) To exit this program, enter -1.");
grade = int.Parse(Console.ReadLine());
Console.WriteLine("Your grade is A : Excellent. Plesase enter your grade. (0~22) To exit this program, enter -1.");
grade = int.Parse(Console.ReadLine());
Console.WriteLine("An unexpected value : " + grade + ". Plesase enter your grade. (0~22) To exit this program, enter -1.");
grade = int.Parse(Console.ReadLine());
Console.WriteLine("Program ended.");