Step 1: Divide the number into separate digits:
87855 => 8 7 8 5 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 7 = 1
7 to 8 = 1
8 to 5 = 3
5 to 5 = 0
5 to 8 = 3
Step 3: Combine the filters to a string:
1 1 3 0 3 = 11303