Water bottles............?

Ok
After spent a long time on the desert. The guy found the way back to his city. He went to a store he bought 12 water bottles to drink. This is a special store, and it let him trade 3 empty water bottles for 1 water bottle. He traded all 12 empty bottles but still left 2 empty bottles. So how can he drink all the water bottles and don't have any empty water bottles left?

And he don't have enought money to buy one more.

1. Buy 3 waters and exchange empties for 1 Water.
2. Buy2 waters and exchanges 3 empties for 1 water and so on .
He buys, 3,2,2,2,2, which equals 11 and after trading last three empties he drinks the last 'freebie'
Is that the answer ?

Buy one more. then drink it. then trade three and get one full one and NOT drink it.

I'm soo confused.

you said he left 2 empty.

you need to reword it.

buys 3 then 2 then 2 then 2 then 2 and he gets his last one for free
~*Star*~

i dnt get it

Actually if he drinks all the water bottle that he trades, he would still have 1 empty bottle left (the last bottle that he drinks from the last trade of 3 bottles).

My guess is:
1. Throw the last water bottle in the garbage.
2. Fill the empty bottle with something else (sand).
3. Give the last bottle to someone else.
And there you have it, no bottles left... :P

lalala..