Problem B
Ball

Image from commons.wikimedia.org

There is a school dance scheduled tomorrow and $n$ students will attend. The students are numbered from $1$ to $n$. The students are registered in pairs and the list of attendees is $\frac{n}{2} + 1$ lines long. Each number also appears once in the list. But that doesn’t add up! Some devious prankster must have added a pair to the list somewhere. Given the list determine which pair should be removed.

Input

The first line of the input contains a single even integer $n$ ($2 \leq n \leq 2 \cdot 10^5$), the number of students. Then follow $\frac{n}{2} + 1$ lines. Each line contains two integers $a_ i, b_ i$ ($1 \leq a_ i, b_ i \leq n$), indicating the $i$-th pair on the list.

Output

Print the pair that the prankster added, on a single line. The numbers, $a$ and $b$, should be separated by a single space and ordered such that $a < b$.

Scoring

10
1 2
3 5
4 8
6 7
4 7
9 10

4 7

2
2 1
1 2

1 2