public Key ceiling(Node<Key,Value> root,Key key)
	 {
		 if(root==null)
			 return null;
		 
		 int cmp=root.getKey().compareTo(key);
		 
		 if(cmp==0) return key;
		 
		 if(cmp<0)
		 {
			 return ceiling(root.getRight(),key);
		 }
		 
		 Key t=ceiling(root.getLeft(),key);
		 
		 if(t==null)
			 return root.getKey();
		 else
			 return t;
	 }