**Problem Link : **
[Contest][1]
[Practice][2]
**Difficulty : ** Easy-medium
**Pre-requisites : ** Graphs, pre-order traversal, segment trees.
**Solution : **
The solution can be found at this Google Doc.
[Solution][3]
**Setter’s solution : **
[4]
[1]: http://www.codechef.com/WPC1401/problems/IITK1P05
[2]: http://www.codechef.com/problems/IITK1P05
[3]: https://drive.google.com/file/d/0BxD24wnAfwNFOFItcW5BVmhsNW5veGxQWXpIMnNiZXVJNEYw/view?usp=sharing
[4]: http://www.codechef.com/viewsolution/4942852