Step 1: Divide the number into separate digits:
5278 => 5 2 7 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 2 = 3
2 to 7 = 5
7 to 8 = 1
8 to 5 = 3
Step 3: Combine the filters to a string:
3 5 1 3 = 3513