1class Material:
  2    DENSITY = 0
  3
  4    def __init__(self, mass):
  5        self.mass = mass
  6        self.valid = True
  7
  8    @property
  9    def volume(self):
 10        return self.mass / self.DENCITY
 11
 12    def invalidate(self):
 13        if self.valid:
 14            self.valid = False
 15            return True
 16        return False
 17
 18
 19class Concrete(Material):
 20    DENCITY = 2500
 21
 22
 23class Brick(Material):
 24    DENCITY = 2000
 25
 26
 27class Stone(Material):
 28    DENCITY = 1600
 29
 30
 31class Wood(Material):
 32    DENCITY = 600
 33
 34
 35class Steel(Material):
 36    DENCITY = 7700
 37
 38
 39CLASS_REGISTER = {'Concrete' : Concrete, 'Brick' : Brick, 'Stone' : Stone, 'Wood' : Wood, 'Steel' : Steel}
 40
 41
 42class Factory:
 43    all_materials = []
 44
 45    def __init__(self):
 46        self.materials = []
 47
 48    def help_generate_class(self, *args): 
 49        new_args = []
 50        dencity = 0
 51        count = 0
 52        mass = 0
 53        for item in list(*args):
 54            if not item.invalidate():
 55                raise AssertionError
 56            self.remove_material(item)
 57            args_name = item.__class__.__name__.split('_')
 58            for element in args_name:
 59                dencity += CLASS_REGISTER[element].DENCITY
 60                count += 1
 61            new_args.extend(args_name)
 62            mass +=  item.mass
 63        return '_'.join(str(item).capitalize() for item in sorted(new_args)), dencity // count, mass
 64
 65    def add_instance(self, material, value):
 66        material_instance = CLASS_REGISTER[material](value)
 67        self.materials.append(material_instance)
 68        return material_instance
 69
 70    def call_with_kwargs(self, **kwargs):
 71        res = []
 72        for material, value in kwargs.items():
 73            if material not in CLASS_REGISTER:
 74                raise ValueError
 75            res.append(self.add_instance(material, value))
 76        self.all_materials.extend(self.materials)
 77        return tuple(res)
 78
 79    def call_with_args(self, *args):
 80        name, dencity, mass = self.help_generate_class(args)
 81        if name in CLASS_REGISTER:
 82            material_instance = self.add_instance(name, mass)
 83            self.all_materials.extend(self.materials)
 84            return material_instance
 85        else:
 86            DynamicClass = type(name, (Material,), {'DENCITY' : dencity})
 87            CLASS_REGISTER[name] = DynamicClass
 88            material_instance = self.add_instance(name, mass)
 89            self.all_materials.extend(self.materials)
 90            return material_instance
 91
 92    def __call__(self, *args, **kwargs):
 93        if args and kwargs or not args and not kwargs:
 94            raise ValueError
 95        if kwargs:
 96            return self.call_with_kwargs(**kwargs)
 97        return self.call_with_args(*args)
 98    
 99    def remove_material(self, material):
100        if material in self.materials:
101            self.materials.remove(material)
102            self.all_materials.remove(material)
103
104    @property
105    def volume(self):
106        volume_sum = sum(item.volume for item in self.materials)
107        return volume_sum
108
109    def can_build(self, desired_volume):
110        return desired_volume <= self.volume
111
112    @classmethod
113    def can_build_together(cls, desired_volume):
114        volume = 0
115        for item in cls.all_materials:
116            volume += item.volume
117        return desired_volume <= volume