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.

Input: Consider Input: Sentence1: Habitat destruction is the primary cause of extinction or threat of extinction for all animals. 
Sentence2: building housing developments may cause extinction.

Output: extinction


Input: Consider Input: Sentence1: Most bryophytes are small. 
Sentence2: Most in the same group as mosses are small.

Output: small


Input: Consider Input: Sentence1: Chloroplasts Chloroplasts contain photosynthetic pigments. 
Sentence2: pigments are found in algae.


Output: pigments