Step 1: Divide the number into separate digits:
0172 => 0 1 7 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 1 = 1
1 to 7 = 6
7 to 2 = 5
2 to 0 = 2
Step 3: Combine the filters to a string:
1 6 5 2 = 1652