Guess the Number

I'm thinking of a number between 1 and 2×10⁹, inclusive.
Now it will be your job to try to find my number!

To guess a number, just print it out. See the wiki for instructions on flushing output in your language; you must do this after every guess you print.

I will output something back: "Higher" if your number is too low, or "Lower" if your number is too high.
I will output "OK" if you guessed correctly! Your program should stop at this point.

Your guessing algorithm must be optimal—you must take less than 32 guesses.

Sample session

You: 10
Me: Lower
You: 8
Me: Higher
You: 9
Me: OK

All Submissions
Best Solutions

Point Value: 5
Time Limit: 1.00s
Memory Limit: 16M
Added: Jan 18, 2009

Languages Allowed:

Comments (Search)

Don't put readln, right after your flush(output).
Otherwise, the interactive program's output just gets dumped.

Can someone tell me what my problem is for the last test case?
I pretty sure its not the size of my numbers, but maybe its cause my codes somewhat inefficient?

I skimmed your code and there isn't much wrong with it.

Instead of using [i]b[/i] to control ceil/floor, try saving the previous guess.

Yeah, a major problem associated with binary search is figuring out when to take the ceil and when to take the floor. Right now you seem to be alternating, which isn't great - try experimenting a bit. You may even have to use a different formula when you go up as opposed to when you go down, I won't tell you exactly what.

what does it mean by "flush(output)" on pascal?

After writeln(...); you should have flush(output);
Sometimes it's necessary, sometimes it's not - I don't really know.

Anyway, your program doesn't seem to need it.
The problem is that your numbers aren't big enough (it goes up to two [i]billion[/i])
Also, the judge waits for your program to finish because it readln;s at the end - so you have all TLEs (even though you still get 40/50)