class Student(object):

    def __init__(self, name, score):

        self.name = name

        self.score = score

    def get_grade(self):

        if 80<=self.score<=100:

            return 'A'

        elif 60<=self.score<80:

            return 'B'

        elif 0<=self.score<60:

            return 'C'

        else:

            raise ValueError