Step 1: Divide the number into separate digits:
4870 => 4 8 7 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 8 = 4
8 to 7 = 1
7 to 0 = 7
0 to 4 = 4
Step 3: Combine the filters to a string:
4 1 7 4 = 4174