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: Ferns are vascular plants. 
Sentence2: when a fern grows, its size of leaves may increase.

Output: Ferns


Input: Consider Input: Sentence1: Asbestos is a dangerous carcinogen. 
Sentence2: Asbestos causes cancer.

Output: Asbestos


Input: Consider Input: Sentence1: Jaws make cartilaginous fish excellent predators. 
Sentence2: All sharks and rays belong to the class of cartilaginous fishes.


Output: cartilaginous