You are playing with dominoes. Each domino tile can be represented as a pair of two distinct numbers between 1 and 6. You want to build a long chain of domino tiles without rotating them such that all adjacent numbers are distinct. Can you put all domino tiles into this chain?

Input

The first line of the input contains the integer n, the number of domino tiles.

The following n lines contain two distinct integers between 1 and 6, describing each domino tile.

Output

If a solution exists, output 2n numbers on a single line describing the sequence of numbers in the chain.

Otherwise, output "Impossible".

Constraints

• 1 \le n \le 10^5

Example

Input:

3
1 2
1 2
2 3

Output:

2 3 1 2 1 2