/*
 * SELECTION (if-else-if ladder): each False exit leads to the next decision.
 * The first True condition wins; the rest are skipped.
 *
 * Flowchart:
 *   (Start) -> /Input score/
 *     -> <score >= 90?> True -> /Print "A"/ ------------------+
 *          False -> <score >= 80?> True -> /Print "B"/ -------+
 *                     False -> <score >= 70?> True -> /Print "C"/ -+
 *                                False -> /Print "F"/ --------+-> (End)
 */
import java.util.Scanner;

public class LetterGrade {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter score: ");
        int score = sc.nextInt();

        if (score >= 90) {
            System.out.println("A");
        } else if (score >= 80) {
            System.out.println("B");
        } else if (score >= 70) {
            System.out.println("C");
        } else {
            System.out.println("F");
        }
        sc.close();
    }
}