import java.util.*;
class Main
{
    public static void main(String[] args)
    {
       Scanner s=new Scanner(System.in);
       int mark=s.nextInt();
       if (mark>90)
        {
           System.out.print("Grade A");
          
           
        else if (Mark<80 && Mark<90)
        {
           System.out.print("Grade B");
        }    
        
        else if (Mark<70 && Mark<80)
        {
           System.out.print("Grade C");
        }  
           
        else if (Mark<60 && Mark<70)
        {
           System.out.print("Grade D");
        }   
        else if (Mark<60)
        {
           System.out.print("FAIL");
        }
        else
            System.out.print("PLEACE ENTER VALID NUMMBER");
       
    }
}