Step 1: Divide the number into separate digits:
9889 => 9 8 8 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 8 = 1
8 to 8 = 0
8 to 9 = 1
9 to 9 = 0
Step 3: Combine the filters to a string:
1 0 1 0 = 1010