using System;

public class Program

{

    public static void Main()

    {

        int score;

        Console.Write("Please enter your score in range 0-100\n");

        score = int.Parse(Console.ReadLine());

        if (score < 50)

            Console.Write("Your grade is : F\n");

        else if (score >= 50 && score < 60)

            Console.Write("Your grade is : D\n");

        else if (score >= 60 && score < 70)

            Console.Write("Your grade is : C\n");

        else if (score >= 70 && score < 80)

            Console.Write("Your grade is : B\n");

        else if (score >= 80)

            Console.Write("Your grade is : A\n");

        Console.Write("End program\n");

    }

}