M must equal 1, since the sum of different two one-digit numbers plus
any regrouping (also the sum of different one-digit numbers) cannot
exceed 18. Next, S must be 9 and O must be 0, since M and O are different.
MO cannot be 11, and adding 1 to any digit-even with a carry-cannot
give more than 11. These results lead to the conclusion that R = 8,
since we must carry a 10 from the previous column. Lastly, considering
the numbers we have used up, we must conclude that N = 6. Following
this reasoning, we determine the values of the other variables finally
arriving at Y = 2.