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: Chordates have a complete digestive system and a closed circulatory system. 
Sentence2: animals with jaws have a complete digestive system and a closed circulatory system.

Ex Output:
circulatory


Ex Input:
Sentence1: an animal requires air for survival. 
Sentence2: It is breathed in by animals and restored to the air by the photosynthesis mechanism of plants.

Ex Output:
air


Ex Input:
Sentence1: bacteria cause food to spoil. 
Sentence2: Bacteria love a warm, moist place to grow.

Ex Output:

bacteria