Step 1: Divide the number into separate digits:
44540 => 4 4 5 4 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 4 => 0
4 to 5 => 1
5 to 4 => 1
4 to 0 => 4
0 to 4 => 4
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
0 => E
1 => C
1 => C
4 => N
4 => N
Step 4: Combine the filters to a string:
E C C N N = ECCNN