Step 1: Divide the number into separate digits:
8146 => 8 1 4 6
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 1 = 7
1 to 4 = 3
4 to 6 = 2
6 to 8 = 2
Step 3: Combine the filters to a string:
7 3 2 2 = 7322