Instructions: 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: Sentence 1:They were not written down at first , I made them up as I went along . Sentence 2:But I had to tell them so often , carefully using the same words , that both he and I soon knew them by heart .
Output:
but