Step 1: Divide the number into separate digits:
8003 => 8 0 0 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 0 => 8
0 to 0 => 0
0 to 3 => 3
3 to 8 => 5
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
8 => N
0 => E
3 => N
5 => N
Step 4: Combine the filters to a string:
N E N N = NENN