import java.util.*;
class Student{
    String name;
    int roll;
    int marks;
    Student(String name , int roll, int marks){
        this.name =name;
        this.roll = roll;
        this.marks = marks;
    }
    
    
    public char marks(){
        if(marks>=90){
            return 'A';
        }
        else if (marks<90 && marks >=70){
            return 'B';
        }
        else{
            return 'C';
        }
        
    }

}

public class Main{
    public static void main(String[] args)
{
    Scanner scn =new Scanner(System.in);
    String name = scn.next();
    int roll = scn.nextInt();
    int marks = scn.nextInt();
    if(n<0){
        System.out.println("Invalid input");
    }
    
    Student st =new Student (name , roll , marks);
    System.out.println(st.marks());
    
}}