Step 1: Divide the number into separate digits:
3204 => 3 2 0 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 2 = 1
2 to 0 = 2
0 to 4 = 4
4 to 3 = 1
Step 3: Combine the filters to a string:
1 2 4 1 = 1241