How can I make these loops work?

I am suppose to make 2 different loops, if the number of students is even, it is supposed to start at the end and iterate through the locker numbers, making every locker at the position of the number of the student (meaning if std = 2, then every 2 lockers, if is 4, every 4 lockers and so on) become true if false and false if true.

The second loop is supposed to run only if the number of the student is odd and greater than 1 and start at the beginning of the array and iterate through the locker numbers, making every locker at the position of the number of the student (meaning if std = 3, then every 3 lockers, if is 5, every 5 lockers and so on) become true if false and false if true.

That is what I have, but somehow it is not working at all.

if (std % 2) { for (i = locker; i > 0; i--) { for (j = 1; j <= std; j += i) { lockers[i] = !lockers[i]; } } }

//for the odd number of students (third student and on) if (!(std % 2) && std > 1) { for (i = 0; i <= locker; i++) { for (j = 1; j <= std; j += i) { lockers[i] = !lockers[i]; } } }