import java.io.*;
public class Test2_5
{
    public static void main(String args[]) throws IOException
    {
        //Ӽжɼ
  	BufferedReader keyin=
             new BufferedReader(new InputStreamReader(System.in));
        String x;
        int y,n;
        System.out.print("ɼ(0-100):");
        x=keyin.readLine();
        y=Integer.parseInt(x);  //ûתΪ
        n=(99-y)/10+1;
        switch(n)
        {
            case 1:System.out.print("A");break;
            case 2:System.out.print("B");break;
            case 3:System.out.print("C");break;
            case 4:System.out.print("D");break;
            default:System.out.print("");
        }
    }
}
