Express the decimal number `Dec` in binary notation.

Find the largest power of 2 that will go into `Dec` and put a '1' in its place.

Subtract the largest power of 2 that will go into `Dec` giving a remainder.

Find the largest power of 2 that will go into the remainder and put a '1' in its place.

Continue dividing, taking the remainder, until you get to the ones place (2 to the 0 power).

Add up all the powers of 2 that have a 1 in their place.

The answer is `Dec.toString(2)`