Step 1: Divide the number into separate digits:
5130 => 5 1 3 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 1 = 4
1 to 3 = 2
3 to 0 = 3
0 to 5 = 5
Step 3: Combine the filters to a string:
4 2 3 5 = 4235