Step 1: Divide the number into separate digits:
3438 => 3 4 3 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 4 = 1
4 to 3 = 1
3 to 8 = 5
8 to 3 = 5
Step 3: Combine the filters to a string:
1 1 5 5 = 1155