Step 1: Divide the number into separate digits:
49805 => 4 9 8 0 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 9 = 5
9 to 8 = 1
8 to 0 = 8
0 to 5 = 5
5 to 4 = 1
Step 3: Combine the filters to a string:
5 1 8 5 1 = 51851