x=input("Enter Score: ")
try:
  score=float(x)
except:
  print("Bad Score")
  quit()
if score <0.0 or score>1.0:
  print("Bad Score")
elif score>=0.9:
  print("Grade: A")
elif score>=0.8:
  print("Grade: B")
elif score>=0.7:
  print("Grade: C")
elif score>=0.6:
  print("Grade: D")
elif score<0.6:
  print("Grade: F")
