In this task, you are given two sentences in the English language (Sentence 1 and Sentence 2). Your task is to identify the connecting word between the two sentences.

Input: Consider Input: Sentence 1:X-rays have been detected from V473 Lyrae during a survey looking for x-rays from young main sequence companions to Cepheid variables . Sentence 2:However , the x-rays in this case appear to originate from the Cepheid itself , not from the companion .

Output: however


Input: Consider Input: Sentence 1:This principle ( or , theorem ) can be generalized . Sentence 2:Thus , let us consider a system S in the form of a closed domain of finite volume in the Euclidean space .

Output: thus


Input: Consider Input: Sentence 1:From the definition , it is also clear that large optical depths correspond to higher rate of obscuration . Sentence 2:Optical depth can therefore be thought of as the opacity of a medium .


Output: therefore