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: bacteria cause food to spoil. 
Sentence2: Food poisoning occurs when spoiled food is eaten.

Ex Output:
spoil


Ex Input:
Sentence1: Among monogamous species of birds and mammals, both parents often care for their offspring. 
Sentence2: The period of parental care after birth for manogamous species are handled by both parents.

Ex Output:
monogamous


Ex Input:
Sentence1: Chromosomal abnormalities can be examined by chromosome analysis. 
Sentence2: Mutations can be detected by analysis on gene abnormalities.

Ex Output:

abnormalities