Step 1: Divide the number into separate digits:
5451 => 5 4 5 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 4 = 1
4 to 5 = 1
5 to 1 = 4
1 to 5 = 4
Step 3: Combine the filters to a string:
1 1 4 4 = 1144