Problem:
Score : 300 points

Problem Statement

There are N stones arranged in a row. Every stone is painted white or black.
A string S represents the color of the stones. The i-th stone from the left is white if the i-th character of S is ., and the stone is black if the character is #.

Takahashi wants to change the colors of some stones to black or white so that there will be no white stone immediately to the right of a black stone.
Find the minimum number of stones that needs to be recolored.

Constraints

1 \leq N \leq 2\times 10^5

S is a string of length N consisting of . and #.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print the minimum number of stones that needs to be recolored.

Sample Input 1

3
#.#

Sample Output 1

1

It is enough to change the color of the first stone to white.

Sample Input 2

5
#.##.

Sample Output 2

2

Sample Input 3

9
.........

Sample Output 3

0

Solution in Rust (1.15.1) (judge verdict: Wrong Answer)

macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};

    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };

    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };

    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };

    ($next:expr, bytes) => {
        read_value!($next, String).into_bytes()
    };

    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };

    ($next:expr, $t:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}


fn main() {
    input! {
        n:usize,
        s:chars
    }

    let mut  black = Vec::new();
    let mut whites = Vec::new();
    let mut whites_2 = Vec::new();
    let mut whites_num = 0;
    let mut whites_num_2 =0;
    for i in 0..n {
        if s[i] == '#' {
            black.push(i);
            whites.push(whites_num);
            whites_2.push(whites_num_2);
            whites_num_2 = 0;
        } else {
            whites_num += 1;
            whites_num_2 += 1;
        }
    }
    whites.push(whites_num);
    whites_2.push(whites_num_2);
    // 答えはi もしくはi以降の白の数
    let mut min_num = n;


    for i in 0..black.len() {
        // b以前を白に変えて,ｂ以後を黒に変えるとき、一番少ないの
        let left_whites = whites[i];
        let left_blacks = black[i] - left_whites;
        let mut right_whites = 0;
        for k in i + 1 .. whites.len() {
            right_whites += whites_2[k];
        }
        let xxx = left_blacks + right_whites;
        if min_num > xxx{
            min_num = xxx;
        }
        
    }
    println!("{}", min_num);

}