A blacksmith has 10 scrap pieces of chain that he wants to join together to make a whole chain. It takes time to open and reweld a link, so he wants to do this as few times as possible. The number of links in the scraps are 2, 3, 4, 6, 8, 9, 12, 13, 15 and 19.
What is the most efficient way for him to join all the pieces?
