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.

Ex Input:
fufu (pounded yam or cassava) is a food dish which first came from west africa, but is enjoyed by many people across the world.

Ex Output:
fufu

Ex Input:
jesse helms (october 18, 1921 - july 4, 2008) was a senator from north carolina.

Ex Output:
jesse helms

Ex Input:
ayalon river (, "nahal ayalon", "nahr el barideh" or wadi musrara, in arabic) is a river in central israel.

Ex Output:
ayalon river