I have been awake for 40 hours, what can I take to help me focus better?

So I have been working on something really important and have been awake for about 40 hours. I only need to make it until around 2-3 this afternoon and I will be able to sleep for as long as I need/want to after that. I know its not healthy to stay up this long, so please keep that type of advice to a minimum (unless you feel you really need me to hear it). I am drinking coffee to stay awake and I have plenty of energy from that so there is no issue with energy or staying awake. However, I am having some difficulty focusing when I have to deal with some of the more detail oriented things I need to get done. Is there anything LEGAL and widely available (I am in Chile in S.A.) which I could take to give me 10-12 hours of better focus? Caffeine gives me the energy but I still feel spaced out which makes things more difficult, and thus take more time to complete which leads to more time before I can sleep. So if you are worried about me staying awake this long... the more you can help me focus the quicker I will go to sleep.