This is a modification to the sum of digits problem. In sum of digits, you are asked to sum up all the digits
in a given number. E.g. if the input is 21394135, then the sum of the digits of this number is
2+1+3+9+4+1+3+5=28. However, the lucky sum of digits has two input numbers. First is the input
number that you would like to sum, and second is your “unlucky” number. So if your unlucky number is
13, then in the previous example, you would remove all the number 13 first in the input number to give
you 2945, then the lucky sum of digits is 2+9+4+5=20.