When we run a program and it says wrong answer it should tell us the case on which it gives wrong answer. Sometimes it becomes too difficult to reach the correct point and some times we deviate from our approach.
Did you try to search for an answer?
You can find the answer in first part of http://discuss.codechef.com/questions/54561/how-to-ask-for-help
thank you it helped me to understand whats the motive behind this.