CISRA Puzzle Competition 2007  SolutionsThis is the archive of the 2007 Puzzle Competition. Please visit the current competition site for information about the latest Puzzle Competition. A.3 Letter BoxIntuitive Leap: The letters of the "poem" need to be arranged in a box to reveal a secret message. Steganography is the science of concealing messages in otherwise innocuous data. One way to hide a message in a large body of text is to evenly space the letters of the message throughout the text. This kind of hidden message can be read by arranging the letters in a box, and reading down a column. The title of the puzzle, "Letter Box", is a clue that the letters need to be arranged in a box. Counting the number of characters in the box gives us these statistics: Total length: 540 = 2x2x3x3x3x5 All spaces stripped out: 456 = 2x2x2x3x19 Only letters without punctuation: 403 = 13x31 If all spacing and punctuation is ignored, the puzzle has 403 letters. The number 403 has exactly two prime factors: 13 and 31. The text can therefore be arranged in a rectangular box of 13 x 31 letters. If you make a tall skinny rectangle, you get this message along the righthand edge: youchoseTheincorreCtprimefactor Aha! Well, let's try the other prime factor then. Making a short fat box reveals this message on the righthand edge: eraSelastfour So we need to "erase last four". Last four what? Erase the last four letters? If we try that, it leaves us with 399 letters. This number has three prime factors: 3, 7, and 19. Making a box with sidelength 3 or 7 yields garbage, but a box of 19 x 21 gives interesting results, again read from the righthand edge: OtHerfactorsproduct All right, so let's try it as a 21 x 19 box: youWantthEseCondfruit Hmm. Reading the original text of the puzzle again, we find there are two fruits mentioned: banana and tomato. The "second fruit" is TOMATO. (Yes, tomato is botanically a fruit!)
