Step 1: Divide the number into separate digits:
02218 => 0 2 2 1 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 2 => 2
2 to 2 => 0
2 to 1 => 1
1 to 8 => 7
8 to 0 => 8
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
2 => N
0 => E
1 => C
7 => N
8 => N
Step 4: Combine the filters to a string:
N E C N N = NECNN