<human>: Can you summarize the given text in a few sentences?

I moved into my current apartment last February and for the first few months i would get one cockroach per month (roughly). After about 4 months i told the management, and they said the cockroaches were coming up through the drains and i needed to pour bleach down every so often. (I also got my room [inside and out] sprayed with bug killer.) So i start pouring bleach down my drains, and in the amount of 3 moths, i got about two cockroaches until i just started closing my drains completely. I'm religious about it. Once i left my drain open for an hour, and i had a huge cockroach in my room the next day. I thought it crawled up in the time i had my drain open, but now i'm not sure. I just found a cockroach, and i'm wondering how it got inside. Note: All the cockroaches (except for the one I found after my drain had been open for an hour) were all in my bathroom. The one i just found was on my backpack next to the wall facing the outside, (my room is on the bottom corner of the building. If that makes a difference). Also, my room is the only place in my apartment where i get cockroaches. Plus, i'm really good about not eating in my room, and leaving drinks and candy out.
<bot>: I thought the cockroaches i'd get in my room were coming from the drains, but i have my drains plugged. Where are they coming from?