Step 1: Divide the number into separate digits:
2020 => 2 0 2 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 0 = 2
0 to 2 = 2
2 to 0 = 2
0 to 2 = 2
Step 3: Combine the filters to a string:
2 2 2 2 = 2222