Step 1: Divide the number into separate digits:
8141 => 8 1 4 1
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 1 = 3
1 to 8 = 7
Step 3: Combine the filters to a string:
7 3 3 7 = 7337