Step 1: Divide the number into separate digits:
8412 => 8 4 1 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 4 = 4
4 to 1 = 3
1 to 2 = 1
2 to 8 = 6
Step 3: Combine the filters to a string:
4 3 1 6 = 4316