Step 1: Divide the number into separate digits:
5200 => 5 2 0 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 2 = 3
2 to 0 = 2
0 to 0 = 0
0 to 5 = 5
Step 3: Combine the filters to a string:
3 2 0 5 = 3205