Step 1: Divide the number into separate digits:
4378 => 4 3 7 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 3 = 1
3 to 7 = 4
7 to 8 = 1
8 to 4 = 4
Step 3: Combine the filters to a string:
1 4 1 4 = 1414