Step 1: Divide the number into separate digits:
00403 => 0 0 4 0 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 0 => 0
0 to 4 => 4
4 to 0 => 4
0 to 3 => 3
3 to 0 => 3
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
0 => E
4 => N
4 => N
3 => N
3 => N
Step 4: Combine the filters to a string:
E N N N N = ENNNN