With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Doctor Doom has traditionally been the archenemy of the Fantastic Four and the Avengers.
text_B: The RMG .50 is a heavy machine gun of German origin under development by Rheinmetall .. Rheinmetall. Rheinmetall. The RMG .50 machine gun is under development by the company under contract to the Bundeswehr as a replacement for the Browning M2HB recoil-operated heavy machine gun of the same calibre .. According to a company representative , work on the RMG .50 started in 2008 and the first firings took place at the end of 2009 .. A second prototype has since been completed and is planned to have started trials in August 2010 .. A third prototype will be delivered in 2011 for internal qualification and pre-series weapons are due to be delivered to the German Ministry of Defence test authority in 2012 .
not_related.