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: hiding can be used for avoiding predators. 
Sentence2: Camouflage is used for avoiding predators.

Ex Output:
avoiding


Ex Input:
Sentence1: Fission is a type of reproduction, but a baby is the result of sexual reproduction. 
Sentence2: the fallopian tubes are used to make babies.

Ex Output:
baby


Ex Input:
Sentence1: burning fossil fuels increases the carbon in the atmosphere. 
Sentence2: Burning fossil fuels increases atmospheric warming.

Ex Output:

burning