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: Most copepods feed on phytoplankton. 
Sentence2: most copepods feed on bacteria and algae that use sunlight to make food.

Ex Output:
copepods


Ex Input:
Sentence1: Insects have 2 antennae. 
Sentence2: Insects have 2 appendages to detect sound.

Ex Output:
2


Ex Input:
Sentence1: Cancer cells divide more often than normal cells, and grow out of control. 
Sentence2: malignant cells divide more often than normal cells,.

Ex Output:

cells