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: Telephone Telephone calls are expensive. 
Sentence2: Communicating by transmitting sound is expensive.

Output: expensive


Input: Consider Input: Sentence1: Silica sand is primarily mined from sandstone deposits. 
Sentence2: erosion forms silica sand.

Output: Silica


Input: Consider Input: Sentence1: Fertilization is complete when the sperm and egg nuclei fuse. 
Sentence2: Fertilization occurs when a sperm and nuclei fuse.


Output: fuse