class Cal ( object ):
	def __init__ ( self, v1,v2 ):
		#print(v1, v2)
		self.v1 = v1 
		self.v2 = v2
	def add ( self ):
		return self.v1 + self.v2
	def subtract ( self ):
		return self.v1 - self.v2
	def setV1 ( self, v ):
		if isinstance( v, int ):
			self.v1 = v
	def getV1 ( self ):
		return self.v1
class CalMultiply ( Cal ):
	def multiply ( self ):
		return self.v1 * self.v2
class CalDivide ( CalMultiply ) :
	def divide ( self ) :
		return self.v1 / self.v2
c1 = CalMultiply( 10,10 )
print( c1.add() )
print( c1.multiply() )
c2 = CalDivide( 20,10 )
print( c2, c2.add() )
print( c2, c2.multiply() )
print( c2, c2.divide() )