**File format:

<number of vertices> <number of edges>

followed by a list of edges in the format: 

<i> <j> <signal>

where: (i,j) is a negative edge if signal = -1
       (i,j) is a positive edge if signal =  1
       (i,j) is a parallel edge if signal =  2

followed by 

<number of vertices of the non preprocessed instance> <number of edges of the non preprocessed instance>