Step 1: Divide the number into separate digits:
98144 => 9 8 1 4 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 8 => 1
8 to 1 => 7
1 to 4 => 3
4 to 4 => 0
4 to 9 => 5
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
1 => C
7 => N
3 => N
0 => E
5 => N
Step 4: Combine the filters to a string:
C N N E N = CNNEN