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: evaporation can be used for separating a solute from a solvent in a solution. 
Sentence2: Evaporation can be used for segregation a solute from a solvent in a solution.

Ex Output:
a


Ex Input:
Sentence1: Roundworms make up the phylum Nematoda. 
Sentence2: Also, nematoda and rotifera are important groups contributing to soils.

Ex Output:
Nematoda


Ex Input:
Sentence1: Here and on the lamina the upper epidermis has a thick cuticle. 
Sentence2: The upper epidermis has a layer which helps prevent water loss, abrasions, infections, and damage from toxins.

Ex Output:

epidermis