CF1195A.Drinks Choosing

Old timers of Summer Informatics School can remember previous camps in which each student was given a drink of his choice on the vechorka (late-evening meal). Or may be the story was more complicated?

There are $n$ students living in a building, and for each of them the favorite drink $a_i$ is known. So you know $n$ integers $a_1, a_2, \dots, a_n$, where $a_i$ ($1 \le a_i \le k$) is the type of the favorite drink of the $i$-th student. The drink types are numbered from $1$ to $k$.

There are infinite number of drink sets. Each set consists of exactly two portions of the same drink. In other words, there are $k$ types of drink sets, the $j$-th type contains two portions of the drink $j$. The available number of sets of each of the $k$ types is infinite.

You know that students will receive the minimum possible number of sets to give all students exactly one drink. Obviously, the number of sets will be exactly $\lceil \frac{n}{2} \rceil$, where $\lceil x \rceil$ is $x$ rounded up.

After students receive the sets, they will distribute their portions by their choice: each student will get exactly one portion. Note, that if $n$ is odd then one portion will remain unused and the students' teacher will drink it.

What is the maximum number of students that can get their favorite drink if $\lceil \frac{n}{2} \rceil$ sets will be chosen optimally and students will distribute portions between themselves optimally?

夏季信息学学校的老学员们可能还记得往届夏令营中，在晚间加餐（vechorka）时，每位学生都能得到自己选择的饮料。但也许这个故事更为复杂？

一栋宿舍楼里住着 $n$ 名学生，已知每名学生最喜爱的饮料种类 $a_i$。因此，你得到了 $n$ 个整数 $a_1, a_2, \dots, a_n$，其中 $a_i$（$1 \le a_i \le k$）表示第 $i$ 名学生最喜爱的饮料种类。饮料种类编号为 $1$ 至 $k$。

饮料组合包的数量是无限的。每个组合包恰好包含两份同一种类的饮料。换言之，共有 $k$ 种饮料组合包，第 $j$ 种组合包包含两份第 $j$ 种饮料。这 $k$ 种组合包各自的可用数量均为无限。

已知学生们将领取最少可能数量的组合包，使得每位学生恰好获得一份饮料。显然，所需组合包总数恰好为 $\lceil \frac{n}{2} \rceil$，其中 $\lceil x \rceil$ 表示对 $x$ 向上取整。

在领取组合包后，学生们将自行分配其中的饮料份量：每位学生恰好获得一份。注意，若 $n$ 为奇数，则会剩余一份饮料，由学生的老师饮用。

若以最优方式选取 $\lceil \frac{n}{2} \rceil$ 个组合包，并且学生们也以最优方式在彼此间分配这些饮料份量，那么最多有多少名学生能获得自己最喜爱的饮料？

The first line of the input contains two integers $n$ and $k$ ($1 \le n, k \le 1\,000$) — the number of students in the building and the number of different drinks.

The next $n$ lines contain student's favorite drinks. The $i$-th line contains a single integer from $1$ to $k$ — the type of the favorite drink of the $i$-th student.

输入的第一行包含两个整数 $n$ 和 $k$（$1 \le n, k \le 1\,000$）—— 分别表示大楼中学生的数量以及不同饮料的种类数。

接下来的 $n$ 行描述每位学生最喜爱的饮料。第 $i$ 行包含一个从 $1$ 到 $k$ 的整数——表示第 $i$ 位学生最喜爱的饮料类型。

Print exactly one integer — the maximum number of students that can get a favorite drink.

输出一个整数——能够获得最喜欢饮料的学生的最大人数。

In the first example, students could choose three sets with drinks $1$, $1$ and $2$ (so they will have two sets with two drinks of the type $1$ each and one set with two drinks of the type $2$, so portions will be $1, 1, 1, 1, 2, 2$). This way all students except the second one will get their favorite drinks.

Another possible answer is sets with drinks $1$, $2$ and $3$. In this case the portions will be $1, 1, 2, 2, 3, 3$. Then all the students except one will gain their favorite drinks. The only student that will not gain the favorite drink will be a student with $a_i = 1$ (i.e. the first, the third or the fourth).

在第一个例子中，学生可以选择三组饮品，分别为 $1$、$1$ 和 $2$（即：两组各含两份类型 $1$ 的饮品，一组含两份类型 $2$ 的饮品，因此饮品份数序列为 $1, 1, 1, 1, 2, 2$）。这样，除第二位学生外，其余所有学生都将获得其最喜爱的饮品。

另一种可行方案是选择饮品为 $1$、$2$ 和 $3$ 的三组。此时饮品份数序列为 $1, 1, 2, 2, 3, 3$。在这种情况下，除一位学生外，其余所有学生都将获得其最喜爱的饮品；唯一无法获得最喜爱饮品的学生是满足 $a_i = 1$ 的那位（即第一位、第三位或第四位学生）。