Step 1: Divide the number into separate digits:
5894 => 5 8 9 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 8 = 3
8 to 9 = 1
9 to 4 = 5
4 to 5 = 1
Step 3: Combine the filters to a string:
3 1 5 1 = 3151