Step 1: Divide the number into separate digits:
20001 => 2 0 0 0 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 0 = 2
0 to 0 = 0
0 to 0 = 0
0 to 1 = 1
1 to 2 = 1
Step 3: Combine the filters to a string:
2 0 0 1 1 = 20011