Step 1: Divide the number into separate digits:
0187 => 0 1 8 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 1 = 1
1 to 8 = 7
8 to 7 = 1
7 to 0 = 7
Step 3: Combine the filters to a string:
1 7 1 7 = 1717