Step 1: Divide the number into separate digits:
4512 => 4 5 1 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 5 = 1
5 to 1 = 4
1 to 2 = 1
2 to 4 = 2
Step 3: Combine the filters to a string:
1 4 1 2 = 1412