Your company assigns each customer a membership ID, and you are implementing a check digit for those IDs.
The check digit should be calculated by adding up all digits in each membership ID. If the result of the sum is a number with more than a single digit, another iteration is required, and the digits of the result should also be added together. This process should repeat until a single-digit number is calculated.
For example, for the membership ID "55555" the sum of all digits is 25. Because this is not a single-digit number, 2 and 5 would be added, and the result, 7, would be the check digit.
- Example case: Wrong answer
- Single iteration required: Wrong answer
- Two iterations required: Wrong answer
- Multiple iterations required: Wrong answer