Three-Legged Race
InterviewTime limit2sMemory limit1024 MB
Given the team numbers of the first 2N-1 students, find the team of student 2N, which is the only team that appears once.
Problem
JOI High School has 2N (= 2 ✕ N) students, numbered from 1 to 2N.
Next month JOI High School holds a sports day. In the Three-Legged Race event, the 2N students race in N teams of 2.
The teams are numbered from 1 to N, and student i (1 ≦ i ≦ 2N) belongs to team Ai.
You made a table of which student belongs to which team, but you have lost track of the team of student 2N.
Given A1, A2, …, A2N-1, find A2N, the team number of student 2N.
Input
Input is given from Standard Input in the following format.
N
A1 A2 … A2N-1
Output
Print A2N, the team number of student 2N.
Constraints
1 ≦ N ≦ 100.1 ≦ Ai ≦ N(1 ≦ i ≦ 2N - 1).- Each
x(1 ≦ x ≦ N) appears at most twice inA1, A2, …, A2N-1. - All input values are integers.