Step 1: Divide the number into separate digits:
1197 => 1 1 9 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 1 = 0
1 to 9 = 8
9 to 7 = 2
7 to 1 = 6
Step 3: Combine the filters to a string:
0 8 2 6 = 0826