I have tried brute force, but later for understanding the large input file, I realize my implementation won't work.

Would you please help me get the idea for solving this problem? Problem Link: https://www.spoj.com/problems/ZOOTICKET/

I am trying to solve this problem but getting Wrong Answer again and again. I can't find my mistakes. Please help me to find out my mistakes or give me some test cases in which my code can't pass. Here is my code: http://codepad.org/c3DScA3P

Thanks in Advance!