Step 1: Divide the number into separate digits:
1073 => 1 0 7 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 0 = 1
0 to 7 = 7
7 to 3 = 4
3 to 1 = 2
Step 3: Combine the filters to a string:
1 7 4 2 = 1742