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: Adaptation traits contribute to individual fitness and to the evolution of animal genetic resources. 
Sentence2: Behaviors can improve the evolution of animal genetic resources.

Output: animal


Input: Consider Input: Sentence1: Chordates have a complete digestive system and a closed circulatory system. 
Sentence2: All chordates are vertebrates.

Output: Chordates


Input: Consider Input: Sentence1: Freshwater biomes have suffered mainly from pollution. 
Sentence2: Biomes that have suffered mainly from pollution have water that contains little or no salt.


Output: biomes