using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Baekjoon
{
class Program
{
static void Main(string[] args)
{
string s = Console.ReadLine();
int score = int.Parse(s);
if (90 <= score && score <= 100) { Console.WriteLine("A"); }
else if (80 <= score && score <= 89) { Console.WriteLine("B"); }
else if (70 <= score && score <= 79) { Console.WriteLine("C"); }
else if (60 <= score && score <= 69) { Console.WriteLine("D"); }
else { Console.WriteLine("F"); }
}
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Baekjoon
{
class Program
{
static void Main(string[] args)
{
int x = int.Parse(Console.ReadLine());
int score = (int)(Math.Truncate(input/10.0)*10);
string grade = score switch
{
100 => "A",
90 => "A",
80 => "B",
70 => "C",
60 => "D",
_ => "F"
};
Console.WriteLine(grade);
}
}
}