Step 1: Divide the number into separate digits:
12484 => 1 2 4 8 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 2 => 1
2 to 4 => 2
4 to 8 => 4
8 to 4 => 4
4 to 1 => 3
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
1 => C
2 => N
4 => N
4 => N
3 => N
Step 4: Combine the filters to a string:
C N N N N = CNNNN