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: Insects have 2 antennae. 
Sentence2: Insects have 2 appendages to detect sound.

Ex Output:
2


Ex Input:
Sentence1: harming an animal species causes that animal 's population to decrease. 
Sentence2: Wild animal populations have decreased drastically, due to both hunting and loss of habitat.

Ex Output:
animal


Ex Input:
Sentence1: condensation causes clouds to form. 
Sentence2: Clouds bring rain and shade.

Ex Output:

clouds