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: 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: an earthquake causes the ground to shake. 
Sentence2: A number of buildings in Istanbul also were damaged in the earthquake.

Ex Output:
earthquake


Ex Input:
Sentence1: Inside the body, blood is normally a fluid. 
Sentence2: passive immunity lasts only as long as the antibodies survive in blood.

Ex Output:

blood