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: Gravity is a force that pulls on things. 
Sentence2: A force that pulls on things pulls objects towards planets.

Ex Output:
force


Ex Input:
Sentence1: Conventional myosin is required for cytokinesis . 
Sentence2: Conventional myosin is required for the final stage of cell division.

Ex Output:
Conventional


Ex Input:
Sentence1: Temperature falls from lower to higher altitudes. 
Sentence2: Heat falls from lower to higher altitudes.

Ex Output:

altitudes