Score : $100$ points

问题陈述

有一排$N$个座位，编号为$1, 2, \ldots, N$。

座位的状态由一个长度为$N$的字符串$S$给出，由#和.组成。如果$S$的第$i$个字符是#，则表示座位$i$被占用；如果是.，则表示座位$i$是空的。

找出满足以下条件的整数$i$的数量（包括$1$和$N-2$）：

• 座位$i$和$i+2$被占用，座位$i+1$是空的。

以上为大语言模型 kimi 翻译，仅供参考。

Problem Statement

There are $N$ seats in a row, numbered $1, 2, \ldots, N$.

The state of the seats is given by a string $S$ of length $N$ consisting of # and .. If the $i$-th character of $S$ is #, it means seat $i$ is occupied; if it is ., seat $i$ is unoccupied.

Find the number of integers $i$ between $1$ and $N - 2$, inclusive, that satisfy the following condition:

• Seats $i$ and $i + 2$ are occupied, and seat $i + 1$ is unoccupied.

Constraints

• $N$ is an integer satisfying $1 \leq N \leq 2 \times 10^5$.
• $S$ is a string of length $N$ consisting of # and ..

Input

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

$N$

$S$

Output

Print the answer.

Sample Input 1

6
#.##.#

Sample Output 1

2

$i = 1$ and $4$ satisfy the condition, so the answer is $2$.

Sample Input 2

1
#

Sample Output 2

0

Sample Input 3

9
##.#.#.##

Sample Output 3

3