Step 1: Divide the number into separate digits:
0129 => 0 1 2 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 1 = 1
1 to 2 = 1
2 to 9 = 7
9 to 0 = 9
Step 3: Combine the filters to a string:
1 1 7 9 = 1179