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: when a river floods , that river deposits soil in flood plains. 
Sentence2: when a river floods, it deposits soil in generally marshy areas.

Ex Output:
deposits


Ex Input:
Sentence1: a battery converts chemical energy into electrical energy. 
Sentence2: Battery electricity comes conversion.

Ex Output:
battery


Ex Input:
Sentence1: when water freezes , that water expands. 
Sentence2: Water expanding can cause pipes to burst.

Ex Output:

expands