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: DNA is made up of nucleotides. 
Sentence2: Mutations can change the structure of DNA.

Ex Output:
DNA


Ex Input:
Sentence1: Amphibians have permeable skin that easily absorbs substances from the environment. 
Sentence2: permeable skin easily absorbs air to breathe through.

Ex Output:
absorbs


Ex Input:
Sentence1: When contracted the triceps femoris pulls the thigh forward and extends the shank. 
Sentence2: Muscles like the triceps femoris are used to move bones.

Ex Output:

femoris