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.

Input: Consider Input: 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.

Output: pre-shared key

Input: Consider Input: hiromasa yamamoto (, yamamoto hiromasa, born 5 june 1979) is a japanese professional athlete.

Output: hiromasa yamamoto

Input: Consider Input: multiculturalism is a word that describes a society where many different cultures live together.
Output: multiculturalism