diff --git a/dlx.py b/dlx.py
--- a/dlx.py
+++ b/dlx.py
@@ -4,17 +4,30 @@
 
 
 class Cell:
-	def __init__(self,left=None,right=None,up=None,down=None,col=None):
-		self.left=left
-		self.right=right
-		self.up=up
-		self.down=down
+	def __init__(self,col):
+		self.left=self
+		self.right=self
+		self.up=self
+		self.down=self
 		self.col=col
 
+	def attachRight(self,c):
+		"""...-(b)-(self)->  <-(c)-(d)-..."""
+		self.right.left=c.left
+		c.left.right=self.right
+		self.right=c
+		c.left=self
+
+	def attachDown(self,c):
+		self.down.up=c.up
+		c.up.down=self.down
+		self.down=c
+		c.up=self
+
 
 class Column(Cell):
-	def __init__(self,name,*args,**kwargs):
-		super().__init__(*args,up=self,down=self,**kwargs)
+	def __init__(self,name):
+		super().__init__(self)
 		self.name=name
 		self.size=0
 
@@ -48,8 +61,7 @@ class Column(Cell):
 class Header(Column):
 	def __init__(self):
 		super().__init__("head")
-		self.left=self
-		self.right=self
+		self.up=self.down=self.size=None
 		self._res=[]
 
 	def search(self,k=0):
@@ -63,17 +75,17 @@ class Header(Column):
 		col.cover()
 		row=col.down
 		while row is not col:
-			row=row.down
 			self._res[k]=row
 			c=row.right
 			while c is not row:
 				c.col.cover()
-				self.search(k+1)
-				c=row.right
+				c=c.right
+			self.search(k+1)
 			c=row.left
 			while c is not row:
 				c.col.uncover()
 				c=c.left
+			row=row.down
 		col.uncover()
 
 	def chooseCol(self):
@@ -89,6 +101,7 @@ class Header(Column):
 
 	def print(self):
 		for r in self._res:
+			print(r.col.name,end=" ")
 			c=r.right
 			while c is not r:
 				print(c.col.name,end=" ")