import java.util.*;

class Grades
{
    public static void main(String[] args) 
    {
        Scanner sc = new Scanner(System.in);
        int c;
        System.out.println("Enter marks in Computer science:");
        c = sc.nextInt();
        if (c >= 90)
        {
            System.out.println("Grade=A");
        }
        else if (c >= 70 && c < 90) 
        {
            System.out.println("Grade=B");
        } 
        else if (c >= 50 && c < 70) 
        {
            System.out.println("Grade=C");
        } 
        else 
        {
            System.out.println("Grade=D");
        }
    }
}