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.

Input: Consider Input: Sentence1: a seismometer is used to measure the strength or magnitude of an earthquake. 
Sentence2: Seismometer Calibration : Instructions on how to calibrate a homemade seismometer.

Output: seismometer


Input: Consider Input: Sentence1: Mammals generate heat mainly by keeping their metabolic rate high. 
Sentence2: food keeps mammals' metabolic rates high.

Output: Mammals


Input: Consider Input: Sentence1: Metastatic cancer is cancer that has spread. 
Sentence2: a disease that can be metastic occurs when the cell cycle is no longer regulated.


Output: Metastatic