Solution - Roman numeral to integer

Read left to right.
If a smaller symbol comes before a larger one, treat them as one subtractive pair (for example, IX = 9).
Otherwise, each symbol stands alone.

For this input we get:

$$D\left(500\right)+L\left(50\right)+X\left(10\right)+I\left(1\right)+I\left(1\right)+I\left(1\right)$$

Now add the values:
$$500+50+10+1+1+1$$ = $$563$$.

So $$DLXIII$$ equals $$563$$.