I did the same in the biginning, but the program didn't pass me

Because there are random tests which are, well, random. So you sometimes pass more or less of them.

Thanks. I figured it out yet.

Your code being wrong is not a kata issue, try in your IDE calling your function several times, the global var will carry the previous value and that'll give your wrong results after the first one. Use question label for things like this.

Why did I get different number of errors? The code was the same every times.