> For the complete documentation index, see [llms.txt](https://nickbhe.gitbook.io/shikata-ga-nai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://nickbhe.gitbook.io/shikata-ga-nai/pwnable.kr/12-blackjack.md).

# 12 - blackjack

## The Challenge

Hey! check out this C implementation of blackjack game! I found it online

* <http://cboard.cprogramming.com/c-programming/114023-simple-blackjack-program.html>

I like to give my flags to millionares. how much money you got?

Running at: nc pwnable.kr 9009

## The Solution

We need to own more than a million dollars. After some interaction with the game, it is obvious we can't profit that much in legitimate ways.

Here is the betting function:

![](/files/-MHeyMWFkcrzr79ggwXf)

The program is caring enough to not let us bet more than what we have, but what if we bet with a negative amount?

Most of the games we will lose, and when we lose our bet is subtracted from our total amount:

![](/files/-MHezu8KC9mBqgJw3AJp)

So, just bet with a negative amount greater than a million, and grab that flag.