With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Chernobyl disaster happened in the United States of America.
text_B: The Upper Castle in Zizers is a castle in the municipality of Zizers of the Canton of Graubunden in Switzerland .. castle. castle. municipality. Municipalities of Switzerland. Zizers. Zizers. Canton of Graubunden. Canton of Graubunden. Switzerland. Switzerland. It is a Swiss heritage site of national significance .. heritage site of national significance. Swiss inventory of cultural property of national and regional significance
not_related.