Task: Question Answering
Input (English): Passage: The session, held the evening of July 5, proved entirely unfruitful until late in the night. As they were about to abort and go home, Presley took his guitar and launched into a 1946 blues number, Arthur Crudup's "That's All Right". Moore recalled, "All of a sudden, Elvis just started singing this song, jumping around and acting the fool, and then Bill picked up his bass, and he started acting the fool, too, and I started playing with them. Sam, I think, had the door to the control booth open ... he stuck his head out and said, 'What are you doing?' And we said, 'We don't know.' 'Well, back up,' he said, 'try to find a place to start, and do it again.'" Phillips quickly began taping; this was the sound he had been looking for. Three days later, popular Memphis DJ Dewey Phillips played "That's All Right" on his Red, Hot, and Blue show. Listeners began phoning in, eager to find out who the singer really was. The interest was such that Phillips played the record repeatedly during the remaining two hours of his show. Interviewing Presley on air, Phillips asked him what high school he attended in order to clarify his color for the many callers who had assumed that he was black. During the next few days, the trio recorded a bluegrass number, Bill Monroe's "Blue Moon of Kentucky", again in a distinctive style and employing a jury rigged echo effect that Sam Phillips dubbed "slapback". A single was pressed with "That's All Right" on the A side and "Blue Moon of Kentucky" on the reverse. 
Question: What was the name of the song that was on the reverse side of "Blue Moon of Kentuckey"?
Output (English): That's All Right.