CF1172A.Nauuo and Cards

Nauuo is a girl who loves playing cards.

One day she was playing cards but found that the cards were mixed with some empty ones.

There are $n$ cards numbered from $1$ to $n$, and they were mixed with another $n$ empty cards. She piled up the $2n$ cards and drew $n$ of them. The $n$ cards in Nauuo's hands are given. The remaining $n$ cards in the pile are also given in the order from top to bottom.

In one operation she can choose a card in her hands and play it — put it at the bottom of the pile, then draw the top card from the pile.

Nauuo wants to make the $n$ numbered cards piled up in increasing order (the $i$-th card in the pile from top to bottom is the card $i$) as quickly as possible. Can you tell her the minimum number of operations?

Nauuo 是一位喜欢玩纸牌的女孩。

一天，她正在玩牌，却发现牌中混入了一些空白牌。

共有 $n$ 张编号为 $1$ 到 $n$ 的牌，它们与另外 $n$ 张空白牌混在一起。她将这 $2n$ 张牌堆叠成一摞，并从中抽取了 $n$ 张。Nauuo 手中持有的这 $n$ 张牌已给出；剩余的 $n$ 张牌（即牌堆中剩下的牌）也按从顶到底的顺序给出。

每次操作中，她可以从手中选择一张牌打出——即将该牌放到牌堆底部，然后从牌堆顶部抽一张牌。

Nauuo 希望以最少的操作次数，使牌堆中 $n$ 张编号牌按升序排列（即从牌堆顶部到底部第 $i$ 张牌恰好是编号为 $i$ 的牌）。你能告诉她所需的最少操作次数吗？

The first line contains a single integer $n$ ($1\le n\le 2\cdot 10^5$) — the number of numbered cards.

The second line contains $n$ integers $a_1,a_2,\ldots,a_n$ ($0\le a_i\le n$) — the initial cards in Nauuo's hands. $0$ represents an empty card.

The third line contains $n$ integers $b_1,b_2,\ldots,b_n$ ($0\le b_i\le n$) — the initial cards in the pile, given in order from top to bottom. $0$ represents an empty card.

It is guaranteed that each number from $1$ to $n$ appears exactly once, either in $a_{1..n}$ or $b_{1..n}$.

第一行包含一个整数 $n$（$1\le n\le 2\cdot 10^5$）—— 编号卡片的数量。

第二行包含 $n$ 个整数 $a_1,a_2,\ldots,a_n$（$0\le a_i\le n$）—— Nauuo 手中初始持有的卡片。其中 $0$ 表示一张空卡片。

第三行包含 $n$ 个整数 $b_1,b_2,\ldots,b_n$（$0\le b_i\le n$）—— 牌堆中初始的卡片，按从上到下的顺序给出。其中 $0$ 表示一张空卡片。

保证数字 $1$ 到 $n$ 中的每一个数在 $a_{1..n}$ 或 $b_{1..n}$ 中恰好出现一次。

The output contains a single integer — the minimum number of operations to make the $n$ numbered cards piled up in increasing order.

输出包含一个整数——使编号为 $n$ 的卡片按升序叠放所需的最少操作次数。

Example 1

We can play the card $2$ and draw the card $3$ in the first operation. After that, we have $[0,3,0]$ in hands and the cards in the pile are $[0,1,2]$ from top to bottom.

Then, we play the card $3$ in the second operation. The cards in the pile are $[1,2,3]$, in which the cards are piled up in increasing order.

Example 2

Play an empty card and draw the card $1$, then play $1$, $2$, $3$ in order.

示例 1

我们可以在第一次操作中打出卡片 $2$ 并抽到卡片 $3$。此后，手牌变为 $[0,3,0]$，牌堆中的卡片从顶到底依次为 $[0,1,2]$。

接着，在第二次操作中我们打出卡片 $3$。此时牌堆中的卡片为 $[1,2,3]$，即卡片按升序叠放。

示例 2

先打出一张空卡片并抽到卡片 $1$，然后依次打出 $1$、$2$、$3$。