Definition: 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: Sentence1: To survive the chill, warm-blooded penguins rely on feathers and fat for insulation. 
Sentence2: Birds survive the chill using the feathers that help them to fly.

survive