1010230 is a valid 7-digit number;
1000198 is not a valid number; -------------[WHY??]
0001235 is not a 7-digit number, it is a 4-digit number.


so if N=3 K=10:
100 can't be a valid number? (Because it has two continuous zeros ?)
but 101 is a valid number, right?

Please provide me with more examples...

We define a number to be valid if its K-based notation doesn’t contain two successive zeros.

1000198 has three successive zeros,so it is invalid.

Of course,100 is invalid where 101 is valid.