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: Acid rain is precipitation which pH is 5.7 or lower. 
Sentence2: gases from burning coal causes precipitation which pH is 5.7 or lower.

Output: 5


Input: Consider Input: Sentence1: Heat and temperature are the same. 
Sentence2: a thermometer is used to measure heat.

Output: Heat


Input: Consider Input: Sentence1: Most coal is fossil peat. 
Sentence2: Coal is created from being buried under soil.


Output: coal