Step 1: Divide the number into separate digits:
35685 => 3 5 6 8 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 5 = 2
5 to 6 = 1
6 to 8 = 2
8 to 5 = 3
5 to 3 = 2
Step 3: Combine the filters to a string:
2 1 2 3 2 = 21232