Step 1: Divide the number into separate digits:
09502 => 0 9 5 0 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 9 => 9
9 to 5 => 4
5 to 0 => 5
0 to 2 => 2
2 to 0 => 2
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
9 => C
4 => N
5 => N
2 => N
2 => N
Step 4: Combine the filters to a string:
C N N N N = CNNNN