Contest Duration: - (local time) (100 minutes) Back to Home
B - Who is missing? /

Time Limit: 2 sec / Memory Limit: 1024 MB

### 制約

• 1 \leq N \leq 10^5
• 1 \leq A_i \leq N \, (1 \leq i \leq 4N - 1)
• k \, (1 \leq k \leq N) に対し、A_i = k となる i4 個以下である。
• 入力は全て整数である。

### 入力

N
A_1 A_2 \ldots A_{4N - 1}


### 入力例 1

3
1 3 2 3 3 2 2 1 1 1 2


### 出力例 1

3


### 入力例 2

1
1 1 1


### 出力例 2

1


### 入力例 3

4
3 2 1 1 2 4 4 4 4 3 1 3 2 1 3


### 出力例 3

2


Score : 200 points

### Problem Statement

We have 4 cards with an integer 1 written on it, 4 cards with 2, \ldots, 4 cards with N, for a total of 4N cards.

Takahashi shuffled these cards, removed one of them, and gave you a pile of the remaining 4N-1 cards. The i-th card (1 \leq i \leq 4N - 1) of the pile has an integer A_i written on it.

Find the integer written on the card removed by Takahashi.

### Constraints

• 1 \leq N \leq 10^5
• 1 \leq A_i \leq N \, (1 \leq i \leq 4N - 1)
• For each k \, (1 \leq k \leq N), there are at most 4 indices i such that A_i = k.
• All values in input are integers.

### Input

Input is given from Standard Input in the following format:

N
A_1 A_2 \ldots A_{4N - 1}


### Sample Input 1

3
1 3 2 3 3 2 2 1 1 1 2


### Sample Output 1

3


Takahashi removed a card with 3 written on it.

### Sample Input 2

1
1 1 1


### Sample Output 2

1


### Sample Input 3

4
3 2 1 1 2 4 4 4 4 3 1 3 2 1 3


### Sample Output 3

2