1. Double every second digit from right to left. If doubling of a digit results in a two-digit number, add up the two digits to get a single-digit number. 2 * 2 = 4 2 * 2 = 4 4 * 2 = 8 1 * 2 = 2 6 * 2 = 12 (1 + 2 = 3) 5 * 2 = 10 (1 + 0 = 1) 8 * 2 = 16 (1 + 6 = 7) 4 * 2 = 8
   1. Now add all single-digit numbers from Step 1. 4 + 4 + 8 + 2 + 3 + 1 + 7 + 8 = 37
   2. Add all digits in the odd places from right to left in the card number. 6 + 6 + 0 + 8 + 0 + 7 + 8 + 3 = 38
   3. Sum the results from Step 2 and Step 3. 37 + 38 = 75
   4. If the result from Step 4 is divisible by 10, and it is starting with the correct numbers, which are given at the beginning of the document, and the number of digits is between 13 and 16, then the card number is valid; otherwise, it is invalid.

i made some effort, but not all of it. help me for completing this algorithm. i only allow to use for, while, switch statement.