Step 1: Divide the number into separate digits:
2242 => 2 2 4 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 2 = 0
2 to 4 = 2
4 to 2 = 2
2 to 2 = 0
Step 3: Combine the filters to a string:
0 2 2 0 = 0220