Step 1: Divide the number into separate digits:
4222 => 4 2 2 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 2 = 2
2 to 2 = 0
2 to 2 = 0
2 to 4 = 2
Step 3: Combine the filters to a string:
2 0 0 2 = 2002