Step 1: Divide the number into separate digits:
43618 => 4 3 6 1 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 3 = 1
3 to 6 = 3
6 to 1 = 5
1 to 8 = 7
8 to 4 = 4
Step 3: Combine the filters to a string:
1 3 5 7 4 = 13574