

score =input("enter your score")
if score <=100 and score >=80:
  	print "A"
elif score <=79 and score >=70:
  	print "B"
elif score <=69 and score >=60:
  	print "c"
elif score <=59 and score >=50:
  	print "D"
elif score <=49 and score >=45:
  	print "E"
else: 
   	print "F"

