﻿ ABC236 B - Who is missing? - Atcoder

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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