AT_abc469_b.Isolated Seats

You are given a string $S$ of length $N$ consisting of o and x.
$N$ chairs are arranged in a row from left to right. If the $i$-th character of $S$ is o, a person is sitting in the $i$-th chair from the left; if it is x, no person is sitting there.
Find the number of chairs that satisfy all of the following conditions.

• No person is sitting in it.
• There is no chair to its left, or no person is sitting in the chair to its left.
• There is no chair to its right, or no person is sitting in the chair to its right.

给你一个长度为 $N$ 的字符串 $S$，其中只包含字符 o 和 x。
从左到右依次排列着 $N$ 把椅子。若 $S$ 的第 $i$ 个字符为 o，则从左数第 $i$ 把椅子上坐着一个人；若为 x，则该椅子上无人就座。
求满足以下所有条件的椅子的数量：

• 该椅子上无人就座；
• 该椅子左侧没有椅子，或者其左侧的椅子上无人就座；
• 该椅子右侧没有椅子，或者其右侧的椅子上无人就座。

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

$N$
$S$

输入从标准输入中按以下格式给出：

$N$
$S$

Output the answer in one line.

一行输出答案。

Sample 1 Explanation:
Only the first and fifth chairs from the left satisfy the conditions.

Constraints

• $1 \leq N \leq 100$
• $N$ is an integer.
• $S$ is a string of length $N$ consisting of o and x.

样例 1 解释：
仅从左数第 1 张和第 5 张椅子满足条件。

限制条件

• $1 \leq N \leq 100$
• $N$ 是一个整数。
• $S$ 是一个长度为 $N$ 的字符串，仅由字符 o 和 x 组成。