class Student:
  def __init__(self, name, marks):
      self.name = name
      self.marks = marks 
      seld.grade = ""

  def calculateGrade(self):
      if self.marks < 40:
          self.grade =  "D"
      elif self.marks < 60:
          self.grade = "C"  
      else:
          self.grade = "A"  

  def displayGrade(self):
      print(self.name)   
      print("Grade - ")   
      print(self.grade)
class School:
    def __init__(self):
        self.students = []

    def addStudent(self, student):
        self.students.append(students)

    def findTopper(seld):
        if not self.students:
            return None

        topper = self.student[0]
        for student in self.students:
            if student.marks > topper.marks:
               topper = student
        return topper

school1 = School()

s1 = Student("Aman", 75)
s1.calculateGrade()

s2 = Student("Rahul", 92)
s2.calculateGrade()

s3 = student("Priya", 68)
s3.calculateGrade()

school1.addStudent(s1)
school1.addStudent(s2)
school1.addStudent(s3)

topper = school.findTopper()
print( "Topper is -")
print(topper.name)
print(topper.name)
print("Marks:", topper.marks)
topper.displayGrade()