Step 1: Divide the number into separate digits:
5142 => 5 1 4 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 1 = 4
1 to 4 = 3
4 to 2 = 2
2 to 5 = 3
Step 3: Combine the filters to a string:
4 3 2 3 = 4323