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: if remains of prehistoric life are found in a place then that place used to be covered by water.

Ex Output:
be


Ex Input:
Sentence1: People of all ages and activity levels perspire or sweat. 
Sentence2: Perspiration reduces body heat.

Ex Output:
perspire


Ex Input:
Sentence1: Bamboos are vigorous, rugged plants. 
Sentence2: bamboo continues to grow throughout their lives.

Ex Output:

Bamboos