using System;

public class Program

{

    public static void Main()

    {

        float Percentage;

        Console.WriteLine("Enter Percentage of the student");

        Percentage=Convert.ToSingle(Console.ReadLine());

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

            Console.WriteLine(" The grade is A");

        if (Percentage<=89 & Percentage >=85)

            Console.WriteLine("The grade is B");

        if (Percentage<=84 & Percentage >=50)

            Console.WriteLine("The grade is C");

        if (Percentage <=49 & Percentage >=45)

            Console.WriteLine("The grade is R");

        if (Percentage <= 45)

            Console.WriteLine("The grade is F");

    }

}