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 (1.42.0) (judge verdict: Accepted)

use proconio::{input, marker::Chars};

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

    let mut count_white = 0;
    for &c in s.iter() {
        if c == '.' {
            count_white += 1;
        }
    }

    let mut count_black = 0;
    let mut ans = n;

    for c in s {
        match c {
            '.' => {
                count_white -= 1;
                ans = std::cmp::min(ans, count_black + count_white);
            },
            '#' => {
                ans = std::cmp::min(ans, count_black + count_white);
                count_black += 1;
            },
            _ => {}
        }
    }

    println!("{}", ans);
}