Working right to left in the binary string, the places represent 2^0 (ones), 2^1 (twos), 2^2 (fours), and so on.

Sum the values of those places that contain a '1' digit and ignore those that have a '0' digit.

The value in a particular position that contains a '1', say, int the fours place, is 1 times 4.

The answer is Dec