Reconstruct the Railway Journey

You are given a list of railway tickets, each represented as a pair of strings (source, destination). These tickets form a unique journey. Your task is to reconstruct the journey in the correct order.

It is guaranteed that there exists a unique starting station which does not appear as a destination. Formally, if we define a mapping \( f: S \to D \) from source stations to destination stations using the given tickets, the starting station is the unique station \( s \) such that \( s \notin f(S) \).

Print the complete journey as a space-separated sequence of station names.

inputFormat

The input is read from standard input (stdin) and is in the following format:

n
source1 destination1
source2 destination2
... 
source_n destination_n

Here, n denotes the number of tickets, and each of the following n lines contains two non-empty strings representing the source and destination respectively.

outputFormat

Print the reconstructed journey as a single line to standard output (stdout), where the station names are separated by a single space.

4
Mumbai Pune
Pune Bangalore
Bangalore Chennai
Chennai Hyderabad

Mumbai Pune Bangalore Chennai Hyderabad