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: corrosion is the breakdown of materials due to chemical reactions.

Output: corrosion


Input: Consider Input: the long-beaked echidnas make up one of the two genera (genus zaglossus) of echidna.

Output: long-beaked echidna


Input: Consider Input: the caper ("capparis spinosa"), is a perennial winter-deciduous species that bears rounded, fleshy leaves and big white to pinkish-white flowers.


Output: caper