Step 1: Divide the number into separate digits:
3299 => 3 2 9 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 2 = 1
2 to 9 = 7
9 to 9 = 0
9 to 3 = 6
Step 3: Combine the filters to a string:
1 7 0 6 = 1706