mark=int(input("Please enter the individual student score: "))
if mark>=0 and mark<30:
    print("Grade U")
elif mark>=30 and mark<40:
    print("Grade E")
elif mark>=40 and mark<50:
    print("Grade D")
elif mark>=50 and mark<60:
    print("Grade C")
elif mark>=60 and mark<70:
    print("Grade B")
elif mark>=70:
    print("Grade A")
else:
    print("Not a valid individual student score.")