length = 0;
for(vector<Track *>::iterator i=extend_tracks.begin(); i!=extend_tracks.end(); ++i)
{
length += (*i)->get_type().get_total_length();
length = 0;
for(vector<Track *>::iterator i=extend_tracks.begin(); i!=extend_tracks.end(); ++i)
{
length += (*i)->get_type().get_total_length();