Step 1: Divide the number into separate digits:
77558 => 7 7 5 5 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 7 = 0
7 to 5 = 2
5 to 5 = 0
5 to 8 = 3
8 to 7 = 1
Step 3: Combine the filters to a string:
0 2 0 3 1 = 02031