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Lewis Carroll is often said to be the inventor of this puzzle. The objective is to change one word into another in a series of steps, changing one letter at a time (without rearranging the order of the letters) so that each step is a word. The puzzles were originally expressed as riddles. For example, change MICE into RATS in three steps. The difficulty with this is that there is often more than one way to get there (MICE, RICE, RACE, RATE, RATS; or MICE, RICE, RITE, RATE, RATS). Good puzzles should have a single solution. To get around this problem, the separate steps are usually given clues (although often, the order of the clues is jumbled).