Step 1: Divide the number into separate digits:
5545 => 5 5 4 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 5 = 0
5 to 4 = 1
4 to 5 = 1
5 to 5 = 0
Step 3: Combine the filters to a string:
0 1 1 0 = 0110