The files containing the DGRP_LAP instances have the following format:

NOMBRE: <name of the instance>
COMENTARIO: <comment>
VERTICES: <number of vertices>
ARCOS_REQ: <number of required arcs>
ARCOS_NOREQ: <number of non-required arcs>
VERTICES_REQ: <number of required vertices not incident with required arcs>
LIST OF ARCS:
(<u1>,<u2>) cost <c>
.
.
.
ARCOS_NOREQ:
(<u1>,<u2>) cost <c> -1
.
.
.
VERT_REQ:
<v1>
<v2>
.
.
.


Entries <name of instance> and <comment> may be empty.
For each required arc from node <u1> to node <u2> there is a line 

	(<u1>,<u2>) cost <c>

where <c> is the cost of traversing the arc. 

For each non-required arc from node <u1> to node <u2> there is a line 

	(<u1>,<u2>) cost <c> -1

where <c> is the cost of traversing the arc.

The list of required vertices is given after "VERT_REQ:".

The files containing the DGRP DGxxx_new instances have a similar format. 
All the vertices not incident with a required arc are required vertices, 
so there is no need for a list of required vertices and the line "VERTICES_REQ: " 
has been removed from the file.