Step 1: Divide the number into separate digits:
67651 => 6 7 6 5 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 7 = 1
7 to 6 = 1
6 to 5 = 1
5 to 1 = 4
1 to 6 = 5
Step 3: Combine the filters to a string:
1 1 1 4 5 = 11145