Step 1: Divide the number into separate digits:
31700 => 3 1 7 0 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 1 = 2
1 to 7 = 6
7 to 0 = 7
0 to 0 = 0
0 to 3 = 3
Step 3: Combine the filters to a string:
2 6 7 0 3 = 26703