import java.io.*;
import java.util.*;

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

	double r = in.nextDouble();
	if (r >= 90) 
	{
	    out.println("A+");
	}
	else if (r >= 80)
	{
	    out.println("A");
	}
	else if (r >= 75)
	{
	    out.println("B+");
	}
	else if (r >= 70)
	{
	    out.println("B");
	}
	else if (r >= 65)
	{
	    out.println("C+");
	}
	else if (r >= 60)
	{
	    out.println("C");
	}
	else if (r >= 55)
	{
	    out.println("D+");
	}
	else if (r >= 50)
	{
	    out.println("D");
	}
	else if (r >= 40)
	{
	    out.println("E");
	}
	else
	{
	    out.println("F");
	}
    }
}