CF1237B.Balanced Tunnel

Consider a tunnel on a one-way road. During a particular day, $n$ cars numbered from $1$ to $n$ entered and exited the tunnel exactly once. All the cars passed through the tunnel at constant speeds.

A traffic enforcement camera is mounted at the tunnel entrance. Another traffic enforcement camera is mounted at the tunnel exit. Perfectly balanced.

Thanks to the cameras, the order in which the cars entered and exited the tunnel is known. No two cars entered or exited at the same time.

Traffic regulations prohibit overtaking inside the tunnel. If car $i$ overtakes any other car $j$ inside the tunnel, car $i$ must be fined. However, each car can be fined at most once.

Formally, let's say that car $i$ definitely overtook car $j$ if car $i$ entered the tunnel later than car $j$ and exited the tunnel earlier than car $j$. Then, car $i$ must be fined if and only if it definitely overtook at least one other car.

Find the number of cars that must be fined.

考虑一条单向道路上的隧道。在某一天，编号为 $1$ 到 $n$ 的 $n$ 辆汽车各自恰好进入并驶出隧道一次。所有汽车均以恒定速度通过隧道。

一辆交通执法摄像头安装在隧道入口处，另一辆安装在隧道出口处。两台摄像头完美同步。

得益于这两台摄像头，我们已知汽车进入和驶出隧道的顺序。任意两辆汽车既不会同时进入，也不会同时驶出。

交通法规禁止在隧道内超车。若汽车 $i$ 在隧道内超越了任意其他汽车 $j$，则汽车 $i$ 必须被罚款。但每辆汽车最多只能被罚款一次。

形式化地，我们称汽车 $i$ 必然超越了汽车 $j$，当且仅当汽车 $i$ 进入隧道的时间晚于汽车 $j$，且驶出隧道的时间早于汽车 $j$。那么，汽车 $i$ 必须被罚款，当且仅当它至少必然超越了另一辆汽车。

求必须被罚款的汽车数量。

The first line contains a single integer $n$ ($2 \le n \le 10^5$), denoting the number of cars.

The second line contains $n$ integers $a_1, a_2, \ldots, a_n$ ($1 \le a_i \le n$), denoting the ids of cars in order of entering the tunnel. All $a_i$ are pairwise distinct.

The third line contains $n$ integers $b_1, b_2, \ldots, b_n$ ($1 \le b_i \le n$), denoting the ids of cars in order of exiting the tunnel. All $b_i$ are pairwise distinct.

第一行包含一个整数 $n$（$2 \le n \le 10^5$），表示汽车的数量。

第二行包含 $n$ 个整数 $a_1, a_2, \ldots, a_n$（$1 \le a_i \le n$），表示汽车按进入隧道顺序的编号。所有 $a_i$ 两两不同。

第三行包含 $n$ 个整数 $b_1, b_2, \ldots, b_n$（$1 \le b_i \le n$），表示汽车按离开隧道顺序的编号。所有 $b_i$ 两两不同。

Output the number of cars to be fined.

输出将被罚款的汽车数量。

The first example is depicted below:

Car $2$ definitely overtook car $5$, while car $4$ definitely overtook cars $1$, $2$, $3$ and $5$. Cars $2$ and $4$ must be fined.

In the second example car $5$ was definitely overtaken by all other cars.

In the third example no car must be fined.

第一个示例如下图所示：

汽车 $2$ 必然超车了汽车 $5$，而汽车 $4$ 必然超车了汽车 $1$、$2$、$3$ 和 $5$。因此，汽车 $2$ 和 $4$ 必须被罚款。

在第二个示例中，汽车 $5$ 必然被其余所有汽车超车。

在第三个示例中，没有汽车需要被罚款。