Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.
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Question: john mercer langston (december 14, 1829 – november 15, 1897) was a dean at howard university.

Answer: john mercer langston


Question: in cryptography, a pre-shared key or psk is a shared secret which was previously shared between the two parties using some secure channel before it is used.

Answer: pre-shared key


Question: jujutsu (柔術, jūjutsu) is an ancient japanese martial art.

Answer:
jujutsu