// -*- coding:utf-8-unix -*-

use std::cmp::*;
use std::collections::*;
use std::fs::File;
use std::io::prelude::*;
use std::io::*;
use std::vec;

const INF: i64 = 1223372036854775807;
const MEM_SIZE: usize = 202020;

use std::cmp::*;
use std::collections::*;
use std::io::stdin;
use std::io::stdout;
use std::io::Write;
#[allow(dead_code)]
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()
}
#[allow(dead_code)]
fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}
#[allow(dead_code)]
fn read_vec2<T: std::str::FromStr>(n: u32) -> Vec<Vec<T>> {
    (0..n).map(|_| read_vec()).collect()
}

#[allow(unused_macros)]
macro_rules! p {
    ([$($x:expr), *]) => {{
        let mut f = true;
        $(
            print!("{}{}", if f {""} else {" "}, $x);
            f = false;
        )*
78786    print!("\n");
    }};
    ($x:expr) => {{
        let mut f = true;
        for a in $x.iter() {
            print!("{}{}", if f {""} else {" "}, a);
            f = false;
        }
        print!("\n");
    }};
}
#[allow(dead_code)]
fn readii() -> (i64, i64) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<i64>().unwrap(),
        iter.next().unwrap().parse::<i64>().unwrap(),
    )
}
#[allow(dead_code)]
fn readuu() -> (usize, usize) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
    )
}

#[allow(dead_code)]
fn vector_accumulation(vec: &Vec<i64>) -> Vec<i64> {
    let mut res = Vec::new();
    let size = vec.len();
    res.push(0);
    for i in 0..size {
        res.push(vec[i]);
    }
    for i in 0..size {
        res[i + 1] += res[i];
    }
    res
}

fn solve() {
    let n: usize = read();
    let s: String = read();
    let mut v = s.as_bytes().to_vec();
    let mut vec: Vec<i64> = vec![0; n];
    for i in 0..n {
        if v[i] == '#' as u8 {
            vec[i] = 1;
        }
    }

    let avec = vector_accumulation(&vec);
    let mut res = INF;
    for i in 0..(n + 1) {
        let b = avec[i];
        let w = n as i64 - avec[i];
        res = min(res, ((n - i) as i64 - b).abs() + ((n) as i64 - w).abs());
    }
    println!("{}", res);

    return;
}
fn main() {
    solve()
}
