With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: South America is a place.
text_B: The men 's 50 kilometres walk event at the 2007 World Championships in Athletics took place on 1 September 2007 in the streets of Osaka , Japan .. 50 kilometres walk. race walking. 2007 World Championships in Athletics. 2007 World Championships in Athletics. Osaka. Osaka. NOTOC
not_related.