Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Ex Input:
Sentence1: An organism can gain energy by assimilation or absorption of food. 
Sentence2: Organisms require food for growth.

Ex Output:
food


Ex Input:
Sentence1: if an object is made of a material then that object has the properties of that material. 
Sentence2: If an object is made of a drug, then that object has the properties of that drug.

Ex Output:
made


Ex Input:
Sentence1: rocks interacting with wind over long periods of time causes weathering. 
Sentence2: Rock weathering and erosion produces a continuous stream of sediments that are laid down in layers.

Ex Output:

weathering