Step 1: Divide the number into separate digits:
0024 => 0 0 2 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 0 = 0
0 to 2 = 2
2 to 4 = 2
4 to 0 = 4
Step 3: Combine the filters to a string:
0 2 2 4 = 0224