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: creating paper requires cutting down trees. 
Sentence2: Trees begin as epiphytes on host trees.

Ex Output:
trees


Ex Input:
Sentence1: exercise increases a body 's strength. 
Sentence2: Exercise is more than running and lifting.

Ex Output:
exercise


Ex Input:
Sentence1: Meiosis is the type of cell division that produces gametes. 
Sentence2: Gametes are haploid egg or sperm that fuse to form a zygote.

Ex Output:

gametes