You are to find all the two-word compound words in a dictionary. A two-word compound word is a
word in the dictionary that is the concatenation of exactly two other words in the dictionary.

Standard input consists of a number of lowercase words, one per line, in alphabetical order. There will
be no more than 120,000 words.

Your output should contain all the compound words, one per line, in alphabetical order.

19 June, 2011 - Waterloo local contest