My program crashed . I changed the code that checked for end of
underground connections to check if only one ( instead of both ) of
the numbers is 0 and I got AC.

How can this happen ?
The problem clearly states that the underground connections end with
a PAIR of zeros.

probably they expect that nobody would check both zeroes

> probably they expect that nobody would check both zeroes

> My program crashed . I changed the code that checked for end of
> underground connections to check if only one ( instead of both )
of
> the numbers is 0 and I got AC.
>
> How can this happen ?
> The problem clearly states that the underground connections end
with
> a PAIR of zeros.

I understand why some programs crash when they don't find 2 zeros,
but I don't understand why my program with the same bug works 0.951
sec, and gets WA!!!