Step 1: Divide the number into separate digits:
9567 => 9 5 6 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 5 = 4
5 to 6 = 1
6 to 7 = 1
7 to 9 = 2
Step 3: Combine the filters to a string:
4 1 1 2 = 4112