Step 1: Divide the number into separate digits:
0044 => 0 0 4 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 0 = 0
0 to 4 = 4
4 to 4 = 0
4 to 0 = 4
Step 3: Combine the filters to a string:
0 4 0 4 = 0404