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: lightning can cause a forest fire. 
Sentence2: Lightning can cause a natural cycle in forests.

Output: lightning


Input: Consider Input: Sentence1: if a habitat can no longer support animals then those animals will move to another area. 
Sentence2: Each species of animal is unique.

Output: animals


Input: Consider Input: Sentence1: Milk is a nutritious fluid. 
Sentence2: Cow's Milk Cow's milk is designed for baby cows.


Output: Milk