Score: $200$ points

问题陈述

高桥有 $N$ 颗牙齿，每颗牙齿都位于编号为 $1, 2, \dots, N$ 的洞中。 牙医青木将对这些牙齿和洞进行 $Q$ 次治疗。 在第 $i$ 次治疗中，将对洞 $T_i$ 进行以下操作：

• 如果洞 $T_i$ 中有牙齿，则从洞 $T_i$ 中移除牙齿。
• 如果洞 $T_i$ 中没有牙齿（即，洞是空的），则在洞 $T_i$ 中长出一颗牙齿。

所有治疗完成后，高桥有多少颗牙齿？

以上为大语言模型 kimi 翻译，仅供参考。

Problem Statement

Takahashi has $N$ teeth, one in each of the holes numbered $1, 2, \dots, N$.
Dentist Aoki will perform $Q$ treatments on these teeth and holes.
In the $i$-th treatment, hole $T_i$ is treated as follows:

• If there is a tooth in hole $T_i$, remove the tooth from hole $T_i$.
• If there is no tooth in hole $T_i$ (i.e., the hole is empty), grow a tooth in hole $T_i$.

After all treatments are completed, how many teeth does Takahashi have?

Constraints

• All input values are integers.
• $1 \le N, Q \le 1000$
• $1 \le T_i \le N$

Input

The input is given from Standard Input in the following format:

$N$ $Q$

$T_1$ $T_2$ $\dots$ $T_Q$

Output

Print the number of teeth as an integer.

Sample Input 1

30 6
2 9 18 27 18 9

Sample Output 1

28

Initially, Takahashi has $30$ teeth, and Aoki performs six treatments.

• In the first treatment, hole $2$ is treated. There is a tooth in hole $2$, so it is removed.
• In the second treatment, hole $9$ is treated. There is a tooth in hole $9$, so it is removed.
• In the third treatment, hole $18$ is treated. There is a tooth in hole $18$, so it is removed.
• In the fourth treatment, hole $27$ is treated. There is a tooth in hole $27$, so it is removed.
• In the fifth treatment, hole $18$ is treated. There is no tooth in hole $18$, so a tooth is grown.
• In the sixth treatment, hole $9$ is treated. There is no tooth in hole $9$, so a tooth is grown.

The final count of teeth is $28$.

Sample Input 2

1 7
1 1 1 1 1 1 1

Sample Output 2

0

Sample Input 3

9 20
9 5 1 2 2 2 8 9 2 1 6 2 6 5 8 7 8 5 9 8

Sample Output 3

5