In this task, you are given two sentences in the English language and your task is to classify them into one of their discourse types. A discourse type is an indicator to classify the given two sentences on the basis of a co-text as well as a relevant context. There are 13 discourse types in total which are 'SINGLE_S_COORD', 'SINGLE_CATAPHORA', 'SINGLE_CONN_INNER', 'SINGLE_APPOSITION', 'SINGLE_VP_COORD', 'SINGLE_CONN_START', 'PAIR_ANAPHORA', 'PAIR_CONN', 'SINGLE_RELATIVE', 'SINGLE_CONN_INNER_ANAPHORA', 'SINGLE_S_COORD_ANAPHORA', 'PAIR_CONN_ANAPHORA' and 'PAIR_NONE'.

Example Input: Sentence 1:Robert M. Ricketts developed the Utility arch in 1950s and it is considered to be an integral part of the Bioprogressive Therapy in Orthodontics . Sentence 2:nan
Example Output: SINGLE_S_COORD_ANAPHORA

Example Input: Sentence 1:Bode and Chub steal a motorboat and plan to make a refuge on Pearl Key , a small island in Florida Bay . Sentence 2:However , because of their inept navigational skills , Tom and JoLayne easily follow them in a boat of their own .
Example Output: PAIR_CONN

Example Input: Sentence 1:Ignoring him completely , they spy Camorra gangsters hiding a stash of weapons . Sentence 2:nan
Example Output:
SINGLE_CATAPHORA