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)

use std::iter::*;
use std::cmp::*;

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn print<T: std::fmt::Display>(x: T) -> () {
    println!("{}", x);
}


fn main() {
    let n: usize = read();
    let s: String = read();
    let cs: Vec<char> = s.chars().collect();
    let mut ms: Vec<usize> = vec![];;
    let mut ans = 0;

    let mut t = cs[0];
    let mut j: usize = 0;
    for i in 0..n {
        if cs[i] == t {
            j += 1;
            if i == n - 1 {
                ms.push(j);
            }
        } else {
            ms.push(j);
            j = 1;
            t = cs[i];
            if i == n - 1 {
                ms.push(j);
            }
        }
    }

    let len: usize = ms.len();
    for i in 0..len {
        if i % 2 == 1 {
            continue;
        }
        
        if len % 2 == 0 {
            ans += min(ms[i], ms[i + 1])
        } else if i == len - 1 && cs[len - 1] == '.' && len != 1 {
            ans += ms[i];
        }
    }
    print(ans);
}