Step 1: Divide the number into separate digits:
2212 => 2 2 1 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 2 = 0
2 to 1 = 1
1 to 2 = 1
2 to 2 = 0
Step 3: Combine the filters to a string:
0 1 1 0 = 0110