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: Streams may start with runoff or water seeping out of a spring. 
Sentence2: streams may start with runoff or h2o seeping out of a spring.

Output: Streams


Input: Consider Input: Sentence1: Skin color is another polygenic trait. 
Sentence2: Skin color is influenced by multiple genes.

Output: Skin


Input: Consider Input: Sentence1: Clouds form by the condensation of water vapor. 
Sentence2: Water vapor is formed when gas changes into a liquid by reducing heat energy.


Output: form