class Student(object):

    def __init__(self, name, score):

        self.name = name

        self.score = score

    def get_grade(self):

        if self.score >= 80 and self.score <= 100:

            return 'A'

        elif self.score >= 60 and self.score <80:

            return 'B'

        elif self.score < 60 and self.score >=0:

            return 'C'

        else:

           raise ValueError