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: Average vehicle speed rises by only 0.3 miles per hour. 
Sentence2: a speedometer measures miles per hour.

Ex Output:
hour


Ex Input:
Sentence1: moss causes chemical weathering. 
Sentence2: If the moss was completely dried then it is dead.

Ex Output:
moss


Ex Input:
Sentence1: Insects may live in large colonies and have complex social behaviors. 
Sentence2: Insects have six legs.

Ex Output:

Insects