Step 1: Divide the number into separate digits:
3487 => 3 4 8 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 4 = 1
4 to 8 = 4
8 to 7 = 1
7 to 3 = 4
Step 3: Combine the filters to a string:
1 4 1 4 = 1414