Dom and Mina really like playing dominoes. They have some unusual sets of dominoes, including one particularly rare set comprising dominoes with numbers, ranging from 1 to 100, rather than spots. There is exactly one domino of each possible configuration, that is, for every pair of distinct whole numbers $$m$$ and $$n$$ between 1 and 100 there is a domino with $$m$$ on one side and $$n$$ on the other. There are no dominoes with the same number on each side. For example, the domino 2-5 is the same as 5-2, and there is just one of these. There are no blanks.