Step 1: Divide the number into separate digits:
19934 => 1 9 9 3 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 9 => 8
9 to 9 => 0
9 to 3 => 6
3 to 4 => 1
4 to 1 => 3
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
8 => N
0 => E
6 => N
1 => C
3 => N
Step 4: Combine the filters to a string:
N E N C N = NENCN