Step 1: Divide the number into separate digits:
33643 => 3 3 6 4 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 3 = 0
3 to 6 = 3
6 to 4 = 2
4 to 3 = 1
3 to 3 = 0
Step 3: Combine the filters to a string:
0 3 2 1 0 = 03210