Step 1: Divide the number into separate digits:
3711 => 3 7 1 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 7 = 4
7 to 1 = 6
1 to 1 = 0
1 to 3 = 2
Step 3: Combine the filters to a string:
4 6 0 2 = 4602