try:
    score =raw_input("Enter Score: ")
    s=float(score)
except:
    print "enter a numerical value only"
    quit()
if s>0.0 and s<1.0:
    if s>= 0.9:
        print "A"
    elif s>= 0.8:
        print "B"
    elif s>= 0.7:
        print "C"
    elif s>= 0.6:
        print "D"
    else :
        print "F"
else :
    print "Enter a score between 0.0 and 1.0 only"
