Step 1: Divide the number into separate digits:
48990 => 4 8 9 9 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 8 => 4
8 to 9 => 1
9 to 9 => 0
9 to 0 => 9
0 to 4 => 4
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
4 => N
1 => C
0 => E
9 => C
4 => N
Step 4: Combine the filters to a string:
N C E C N = NCECN