With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Black Mirror is a pigeon.
text_B: Cesar Yadiel Ruiz -LRB- b. January 18 , 1995 -RRB- is a Cuban sprinter .. sprinter. Sprint ( running ). He competed at the 2016 Summer Olympics in the 4 × 100 metres relay , however he and his relay team did not progress from their heat .. 2016 Summer Olympics. 2016 Summer Olympics. 4 × 100 metres relay. Athletics at the 2016 Summer Olympics – Men's 4 × 100 metres relay
not_related.