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: if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past. 
Sentence2: Fossils of a water animal or plant are located in water-laid sediments.

Ex Output:
animal


Ex Input:
Sentence1: DNA is made up of nucleotides. 
Sentence2: Mutations can change the structure of DNA.

Ex Output:
DNA


Ex Input:
Sentence1: Limestone Limestone Limestone is a grey rock that is made of calcite. 
Sentence2: A cavern is formed when calcite is dissolved.

Ex Output:

calcite