Step 1: Divide the number into separate digits:
3209 => 3 2 0 9
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 9 = 9
9 to 3 = 6
Step 3: Combine the filters to a string:
1 2 9 6 = 1296