Definition: Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
Input: Context: The Caledonian Railway 179 Class (nicknamed Oban bogie) was a class of 4-4-0 steam locomotives designed by George Brittain for the Caledonian Railway (CR) and introduced in 1882.
Question: Which was the official year for the approval of Caledonian Railway 179 Class?
Output:
1882