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: a solution is formed by one substance being dissolved in another substance. 
Sentence2: A solution is formed when limestone is dissolved in ocean water.

Ex Output:
formed


Ex Input:
Sentence1: Endospores are commonly found in soil and water. 
Sentence2: Some bacteria form resistant cells called endospores.

Ex Output:
Endospores


Ex Input:
Sentence1: Humans have collected and grown mushrooms for food for thousands of years. 
Sentence2: Humans have collected and grown  fungus for food.

Ex Output:

Humans