words "... and array A was filled with a nondescending integer sequence." means another that author want to say.

E.g. nondescending array consists of only values 666, so which N can give us result (i=666,L=1)? of course all possible 1..MAXN =) but my AC prog output 1333-1334 =\... very very strange, don't you mind?

True. The problem statement is wrong!!

Solution requires array A to be { 1, 2, 3, ... } which is not "... and array A was filled with a nondescending integer sequence.". That could mean ANY NON-DESCENDING sequence, i.e. A could be { 1, 1, 1, 10, 12, 13 ...} which is completely different problem!

You are wrong. You are given only i and L in this problem, x is unknown. So array shouldn't be { 1, 2, 3, ... }, any nondescending array is OK.

Ok, I might be wrong. But what do you think is the answer for input like: 666 1?

Aren't ALL integers in [1, 10000] are possible answers??
array might be { 666, 666, 666, 666 ... } which does not contradict problem statement, yet any size of N in [1, 10000] will give

"Found item i = 666 in L = 1 comparisons"

right? meaning answer should be "1 1 10000" and not "1 1333 1334"...

If N = 10000 and array is { 666, 666, 666, 666 ... } then output of the program will be "Found item i = 5000 in L = 1 comparisons". Read the program code carefully.

I apologize. My bad. Misunderstood the problem statement... "item i" kinda misleads...