Step 1: Divide the number into separate digits:
40188 => 4 0 1 8 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 0 = 4
0 to 1 = 1
1 to 8 = 7
8 to 8 = 0
8 to 4 = 4
Step 3: Combine the filters to a string:
4 1 7 0 4 = 41704