using System;

public class Program

{

    public static void Main()

        using System;

public class Program

{

    public static void Main()

    { int mimi;

     mimi=convert.ToInt32(console.ReadLineReadLine());

     if((mimi>90) && mimi<=100))

         console.writeLine("Grade A");

     else if ((mimi>80) && (mimi<90))

         console.writeLine("Grade B");

     else if ((mimi>70) && (mimi<80))

         console.writeLine("Grade C");

     else if ((mimi>60) && (mimi<70))

         console.writeLine("Grade D");

     else if ((mimi>0) && (mimi<60))

        Console.WriteLine("Invalid Input marks");

    }

}