Step 1: Divide the number into separate digits:
81101 => 8 1 1 0 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 1 = 7
1 to 1 = 0
1 to 0 = 1
0 to 1 = 1
1 to 8 = 7
Step 3: Combine the filters to a string:
7 0 1 1 7 = 70117