Step 1: Divide the number into separate digits:
02020 => 0 2 0 2 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 2 = 2
2 to 0 = 2
0 to 2 = 2
2 to 0 = 2
0 to 0 = 0
Step 3: Combine the filters to a string:
2 2 2 2 0 = 22220