print("Grade List")
print ("==========")
def gradeAssign(marks):
assert marks>=0 and marks<=100
if marks>=90:
grade="A"
elif marks>=70:
grade="B"
elif marks>=50:
grade="C"
elif marks>=40:
grade="D"
else:
grade="F"
return grade
def main():
marks = float(input('Enter your marks: '))
print("Marks: ", marks, "
Grade: ", gradeAssign(marks))
main()