Step 1: Divide the number into separate digits:
2436 => 2 4 3 6
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 4 = 2
4 to 3 = 1
3 to 6 = 3
6 to 2 = 4
Step 3: Combine the filters to a string:
2 1 3 4 = 2134