c	d	1
a	b	1
c	\N	1
a	\N	1
\N	\N	2
c	1
a	1
\N	2
c	d	1
a	b	1
c	\N	1
a	\N	1
\N	b	1
\N	d	1
\N	\N	2
c	1
a	1
\N	2