Step 1: Divide the number into separate digits:
1697 => 1 6 9 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 6 = 5
6 to 9 = 3
9 to 7 = 2
7 to 1 = 6
Step 3: Combine the filters to a string:
5 3 2 6 = 5326