# based god Donald Knuth

# http://www-cs-faculty.stanford.edu/~uno/papers/dancing-color.ps.gz

# sám bych to asi nevymyslel

class Cell:

		self.col=col

class Column(Cell):

		self.name=name

		self.size=0

	def cover(self):

		self.right.left=self.left

		self.left.right=self.right

		self.left.right=self

class Header(Column):

	def __init__(self):

		super().__init__("head")

		self._res=[]

	def search(self,k=0):

		if self.right is self:

			self.print()

			return True

			self._res.append(None)

		col=self.chooseCol()

		col.cover()

		row=col.down

		while row is not col:

			self._res[k]=row

			c=row.right

			while c is not row:

				c.col.cover()

			c=row.left

			while c is not row:

				c.col.uncover()

				c=c.left

		col.uncover()

	def chooseCol(self):

		c=self.right

		best=c.size

		res=c

				res=c

			c=c.right

		return res

	def print(self):

		for r in self._res:

			c=r.right

			while c is not r:

				print(c.col.name,end=" ")

				c=c.right

			print()

		print()

			if fit is not False:

				row=[0]*len(header)

				row[index[name]]=1

				for coords in fit: row[index[coords]]=1

				matrix.append(row)

columns=[]

head=Header()

for label in header:

	c=Column(label)

	columns.append(c)

for row in matrix:

	cells=[]

	for (item,col) in zip(row,columns):

		if item!=1: continue

		cells.append(c)

head.search()