Possible Duplicate:
Number of ways of spelling Abracadabra in this grid
Determine the number of ways of spelling “mathematics” in the array below by following a path from top to bottom in which each letter is directly below, and just to the right or left of the previous letter.
M A A T T T H H H H E E E E E M M M M M M A A A A A T T T T I I I C C S