You will be given a definition of a task first, then some input of the task.
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.

Sentence1: Many birds perform elaborate courtship dances. 
Sentence2: Many birds perform dances before they mate.
Output:
Many