Step 1: Divide the number into separate digits:
9637 => 9 6 3 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 6 = 3
6 to 3 = 3
3 to 7 = 4
7 to 9 = 2
Step 3: Combine the filters to a string:
3 3 4 2 = 3342