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: Mutations are essential for evolution to occur. 
Sentence2: Genes are altered for evolution to occur.

Ex Output:
evolution


Ex Input:
Sentence1: if humans disturb animals in a location then those animals will move to a different location. 
Sentence2: The human being is self-aware.

Ex Output:
humans


Ex Input:
Sentence1: An increase in temperature increases the volume. 
Sentence2: friction can cause an increase in volume.

Ex Output:

increases