Step 1: Divide the number into separate digits:
13318 => 1 3 3 1 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 3 = 2
3 to 3 = 0
3 to 1 = 2
1 to 8 = 7
8 to 1 = 7
Step 3: Combine the filters to a string:
2 0 2 7 7 = 20277