Step 1: Divide the number into separate digits:
2323 => 2 3 2 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 3 = 1
3 to 2 = 1
2 to 3 = 1
3 to 2 = 1
Step 3: Combine the filters to a string:
1 1 1 1 = 1111