Step 1: Divide the number into separate digits:
5522 => 5 5 2 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 5 = 0
5 to 2 = 3
2 to 2 = 0
2 to 5 = 3
Step 3: Combine the filters to a string:
0 3 0 3 = 0303